Frost is a thin layer of

ice Ice is water frozen into a solid state, typically forming at or below temperatures of 0 degrees Celsius or Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaq ...

on a

solid Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...

surface, which forms from

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

in an above-

freezing Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid o ...

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

coming in contact with a solid surface whose temperature is below freezing, and resulting in a

phase change In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic State of ...

from water vapor (a

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

) to ice (a solid) as the water vapor reaches the

freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...

. In

temperate climate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

s, it most commonly appears on surfaces near the ground as fragile white

crystals A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

; in cold climates, it occurs in a greater variety of forms. The propagation of crystal formation occurs by the process of

nucleation In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that deter ...

. The

ice crystals Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. Formation The hugely symmetric shapes are due to depositional growth, na ...

of frost form as the result of

fractal In mathematics, a fractal is a geometric shape containing detailed structure at arbitrarily small scales, usually having a fractal dimension strictly exceeding the topological dimension. Many fractals appear similar at various scales, as illu ...

process development. The depth of

frost crystals Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. Formation The hugely symmetric shapes are due to depositional growth, na ...

varies depending on the amount of time they have been accumulating, and the concentration of the water vapor (

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

). Frost crystals may be invisible (black), clear (

translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions a ...

), or white; if a mass of frost crystals scatters light in all directions, the coating of frost appears white. Types of frost include crystalline frost (

hoar frost Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase transition, phase change from wa ...

or radiation frost) from deposition of water vapor from air of low humidity,

white frost Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase transition, phase change from wa ...

in humid conditions,

window frost Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...

on glass surfaces,

advection frost Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...

from cold wind over cold surfaces,

black frost Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...

without visible ice at low temperatures and very low humidity, and

rime Rime may refer to: *Rime ice, ice that forms when water droplets in fog freeze to the outer surfaces of objects, such as trees Rime is also an alternative spelling of "rhyme" as a noun: *Syllable rime, term used in the study of phonology in ling ...

under

supercooled Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its melting point without it becoming a solid. It achieves this in the absence of a seed crystal or nucleus around which a crystal ...

wet conditions. Plants that have evolved in warmer climates suffer damage when the temperature falls low enough to freeze the water in the

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

that make up the plant tissue. The tissue damage resulting from this process is known as "frost damage".

Farmer A farmer is a person engaged in agriculture, raising living organisms for food or raw materials. The term usually applies to people who do some combination of raising field crops, orchards, vineyards, poultry, or other livestock. A farmer mig ...

s in those regions where frost damage has been known to affect their crops often invest in substantial means to protect their crops from such damage.

Formation

If a solid surface is chilled below the

dew point The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will cond ...

of the surrounding humid air, and the surface itself is colder than freezing, ice will form on it. If the water deposits as a liquid that then freezes, it forms a coating that may look glassy, opaque, or crystalline, depending on its type. Depending on context, that process may also be called

atmospheric icing Atmospheric icing occurs in the atmosphere when water droplets suspended in air freezing, freeze on objects they come in contact with. It is not the same as freezing rain, which is caused directly by precipitation. Icing conditions can be particul ...

. The ice it produces differs in some ways from crystalline frost, which consists of spicules of ice that typically project from the solid surface on which they grow. The main difference between the ice coatings and frost spicules arises because the crystalline spicules grow directly from

desublimation Deposition is the phase transition in which gas transforms into solid without passing through the liquid phase. Deposition is a thermodynamic process. The reverse of deposition is sublimation and hence sometimes deposition is called desublimati ...

of water vapour from air, and desublimation is not a factor in icing of freezing surfaces. For desublimation to proceed, the surface must be below the frost point of the air, meaning that it is sufficiently cold for ice to form without passing through the

liquid phase A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, an ...

. The air must be humid, but not sufficiently humid to permit the condensation of liquid water, or icing will result instead of desublimation. The size of the crystals depends largely on the temperature, the amount of

available, and how long they have been growing undisturbed. As a rule, except in conditions where supercooled droplets are present in the air, frost will form only if the deposition surface is colder than the surrounding air. For instance, frost may be observed around cracks in cold wooden sidewalks when humid air escapes from the warmer ground beneath. Other objects on which frost commonly forms are those with low

specific heat In thermodynamics, the specific heat capacity (symbol ) of a substance is the heat capacity of a sample of the substance divided by the mass of the sample, also sometimes referred to as massic heat capacity. Informally, it is the amount of heat t ...

or high

thermal emissivity The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiation (light) and infrared radiation, which is n ...

, such as blackened metals, hence the accumulation of frost on the heads of rusty nails. The apparently erratic occurrence of frost in adjacent localities is due partly to differences of elevation, the lower areas becoming colder on calm nights. Where static air settles above an area of ground in the absence of wind, the absorptivity and specific heat of the ground strongly influence the temperature that the trapped air attains.

Types

Hoar frost

Hoar frost, also hoarfrost, radiation frost, or pruina, refers to white ice crystals deposited on the ground or loosely attached to exposed objects, such as wires or leaves. They form on cold, clear nights when conditions are such that heat radiates into outer space faster than it can be replaced from nearby warm objects or brought in by the wind. Under suitable circumstances, objects cool to below the frost point of the surrounding air, well below the freezing point of water. Such freezing may be promoted by effects such as flood frost or frost pocket. These occur when ground-level radiation cools air until it flows downhill and accumulates in pockets of very cold air in valleys and hollows. Hoar frost may freeze in such low-lying cold air even when the air temperature a few feet above ground is well above freezing. The word "hoar" comes from an

Old English Old English (, ), or Anglo-Saxon, is the earliest recorded form of the English language, spoken in England and southern and eastern Scotland in the early Middle Ages. It was brought to Great Britain by Anglo-Saxon settlement of Britain, Anglo ...

adjective that means "showing signs of old age". In this context, it refers to the frost that makes trees and bushes look like white hair. Hoar frost may have different names depending on where it forms: *Air hoar is a deposit of hoar frost on objects above the surface, such as tree branches, plant stems, and wires. *Surface hoar refers to fern-like ice crystals directly deposited on snow, ice, or already frozen surfaces. *Crevasse hoar consists of crystals that form in glacial crevasses where water vapour can accumulate under calm weather conditions. *

Depth hoar Depth hoar, also called sugar snow or temperature gradient snow (or TG snow), are large snow-crystals occurring at the base of a snowpack that form when uprising water vapor deposits, or desublimates, onto existing snow crystals. Depth hoar cr ...

refers to faceted crystals that have slowly grown large within cavities beneath the surface of banks of dry snow. Depth hoar crystals grow continuously at the expense of neighbouring smaller crystals, so typically are visibly stepped and have faceted hollows. When surface hoar covers sloping snowbanks, the layer of frost crystals may create an

avalanche An avalanche is a rapid flow of snow down a slope, such as a hill or mountain. Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and earth ...

risk; when heavy layers of new snow cover the frosty surface, furry crystals standing out from the old snow hold off the falling flakes, forming a layer of voids that prevents the new snow layers from bonding strongly to the old snow beneath. Ideal conditions for hoarfrost to form on snow are cold, clear nights, with very light, cold air currents conveying humidity at the right rate for growth of frost crystals. Wind that is too strong or warm destroys the furry crystals, and thereby may permit a stronger bond between the old and new snow layers. However, if the winds are strong enough and cold enough to lay the crystals flat and dry, carpeting the snow with cold, loose crystals without removing or destroying them or letting them warm up and become sticky, then the frost interface between the snow layers may still present an avalanche danger, because the texture of the frost crystals differs from the snow texture, and the dry crystals will not stick to fresh snow. Such conditions still prevent a strong bond between the snow layers. In very low temperatures where fluffy surface hoar crystals form without subsequently being covered with snow, strong winds may break them off, forming a dust of ice particles and blowing them over the surface. The ice dust then may form ''

yukimarimo Yukimarimo are balls of fine frost formed at low temperatures on the Antarctic plateau during weak wind conditions. Yukimarimo were discovered in 1995 at Dome F by the 36th Japanese Antarctic Research Expedition (JARE-36) at temperatures of –59 ...

'', as has been observed in parts of Antarctica, in a process similar to the formation of

dust bunnies Dust bunnies (or dustbunnies) are small clumps of dust that form under furniture and in corners that are not cleaned regularly. They are made of hair, lint, flakes of dead skin, spider webs, dust, and sometimes light rubbish and debris and a ...

and similar structures. Frosted Flower

Hoar frost and

also occur in man-made environments such as in freezers or industrial cold-storage facilities. If such cold spaces or the pipes serving them are not well insulated and are exposed to ambient humidity, the moisture will freeze instantly depending on the freezer temperature. The frost may coat pipes thickly, partly insulating them, but such inefficient insulation still is a source of heat loss.

Advection frost

Advection frost (also called wind frost) refers to tiny ice spikes that form when very cold

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...

is blowing over tree branches, poles, and other surfaces. It looks like rimming on the edges of flowers and leaves, and usually forms against the direction of the wind. It can occur at any hour, day or night.

Window frost

Window frost (also called fern frost or ice flowers) forms when a glass pane is exposed to very cold air on the outside and warmer, moderately moist air on the inside. If the pane is a bad insulator (for example, if it is a single-pane window), water vapour condenses on the glass, forming frost patterns. With very low temperatures outside, frost can appear on the bottom of the window even with double-pane energy-efficient windows because the air convection between two panes of glass ensures that the bottom part of the glazing unit is colder than the top part. On unheated motor vehicles, the frost usually forms on the outside surface of the glass first. The glass surface influences the shape of crystals, so imperfections, scratches, or dust can modify the way ice nucleates. The patterns in window frost form a

with a

fractal dimension In mathematics, more specifically in fractal geometry, a fractal dimension is a ratio providing a statistical index of complexity comparing how detail in a pattern (strictly speaking, a fractal pattern) changes with the scale at which it is meas ...

greater than one, but less than two. This is a consequence of the nucleation process being constrained to unfold in two dimensions, unlike a snowflake, which is shaped by a similar process, but forms in three dimensions and has a fractal dimension greater than two. If the indoor air is very humid, rather than moderately so, water first

condenses Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...

in small droplets, and then freezes into

clear ice Clear ice refers to a solid precipitation which forms when air temperature is between and and there are supercooled, relatively large drops of water (from freezing fog). A rapid accretion and a slow dissipation of latent heat of fusion favor the ...

. Similar patterns of freezing may occur on other smooth vertical surfaces, but they seldom are as obvious or spectacular as on clear glass. File:Frost patterns 1.jpg File:Frost patterns 2.jpg File:Frost patterns 3.jpg File:Frost patterns 4.jpg File:Frost patterns 5.jpg File:Frost patterns 25.jpg File:WindowFrostNewmarketOntario1986.jpg File:Frost on a plastic container in a -30 C freezer.jpg PXL 20210220 150158529

White frost

White frost is a solid deposition of ice that forms directly from water vapour contained in air. White frost forms when relative humidity is above 90% and the temperature below −8 °C (18 °F), and it grows against the wind direction, since air arriving from

windward Windward () and leeward () are terms used to describe the direction of the wind. Windward is ''upwind'' from the point of reference, i.e. towards the direction from which the wind is coming; leeward is ''downwind'' from the point of reference ...

has a higher humidity than leeward air, but the wind must not be strong, else it damages the delicate icy structures as they begin to form. White frost resembles a heavy coating of hoar frost with big, interlocking crystals, usually needle-shaped.

Rime

Rime is a type of ice deposition that occurs quickly, often under heavily humid and windy conditions. Technically speaking, it is not a type of frost, since usually

water drops are involved, in contrast to the formation of hoar frost, in which water vapour desublimates slowly and directly. Ships travelling through Arctic seas may accumulate large quantities of rime on the rigging. Unlike hoar frost, which has a feathery appearance, rime generally has an icy, solid appearance.

Black frost

Black frost or ("killing frost") is not strictly speaking frost at all, because it is the condition seen in crops when the humidity is too low for frost to form, but the temperature falls so low that plant tissues freeze and die, becoming blackened, hence the term "black frost". Black frost often is called "killing frost" because white frost tends to be less cold, partly because the

latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition. Latent heat can be understo ...

of freezing of the water reduces the temperature drop.

Effect on plants

Damage

Many plants can be damaged or killed by freezing temperatures or frost. This varies with the type of plant, the tissue exposed, and how low temperatures get; a "light frost" of damages fewer types of plants than a "hard frost" below . Plants likely to be damaged even by a light frost include vines—such as beans, grapes, squashes, melons—along with

nightshade The Solanaceae , or nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and orna ...

s such as tomatoes, eggplants, and peppers. Plants that may tolerate (or even benefit from) frosts include: *root vegetables (e.g. beets, carrots, parsnips, onions) *leafy greens (e.g. lettuces, spinach, chard, cucumber) *

cruciferous vegetables Cruciferous vegetables are vegetables of the family Brassicaceae (also called Cruciferae) with many genera, species, and cultivars being raised for food production such as cauliflower, cabbage, kale, garden cress, bok choy, broccoli, Brussels spr ...

(e.g. cabbages, cauliflower, bok choy, broccoli, Brussels sprouts, radishes, kale, collard, mustard, turnips, rutabagas) Even those plants that tolerate frost may be damaged once temperatures drop even lower (below ). Hardy perennials, such as ''

Hosta ''Hosta'' (, syn. ''Funkia'') is a genus of plants commonly known as hostas, plantain lilies and occasionally by the Japanese name gibōshi. Hostas are widely cultivated as shade-tolerant foliage plants. The genus is currently placed in the fa ...

'', become dormant after the first frosts and regrow when spring arrives. The entire visible plant may turn completely brown until the spring warmth, or may drop all of its leaves and flowers, leaving the stem and stalk only. Evergreen plants, such as pine trees, withstand frost although all or most growth stops.

Frost crack Frost crack or Southwest canker is a form of tree bark damage sometimes found on thin barked trees, visible as vertical fractures on the southerly facing surfaces of tree trunks. Frost crack is distinct from sun scald and sun crack and physically d ...

is a bark defect caused by a combination of low temperatures and heat from the winter sun. Vegetation is not necessarily damaged when leaf temperatures drop below the freezing point of their cell contents. In the absence of a site

nucleating In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that determ ...

the formation of ice crystals, the leaves remain in a

liquid state, safely reaching temperatures of . However, once frost forms, the leaf

may be damaged by sharp ice crystals. Hardening is the process by which a plant becomes tolerant to low temperatures. See also

Cryobiology Cryobiology is the branch of biology that studies the effects of low temperatures on living things within Earth's cryosphere or in science. The word cryobiology is derived from the Greek words κρῧος ryos "cold", βίος ios "life", and λό ...

. Certain

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, notably ''

Pseudomonas syringae ''Pseudomonas syringae'' is a rod-shaped, Gram-negative bacterium with polar flagella. As a plant pathogen, it can infect a wide range of species, and exists as over 50 different pathovars, all of which are available to researchers from internat ...

'', are particularly effective at triggering frost formation, raising the nucleation temperature to about . Bacteria lacking ice nucleation-active proteins (

ice-minus bacteria Ice-minus bacteria is a common name given to a variant of the common bacterium ''Pseudomonas syringae'' (''P. syringae''). This strain of ''P. syringae'' lacks the ability to produce a certain surface protein, usually found on wild-type ''P. syrin ...

) result in greatly reduced frost damage.

Protection methods

Typical measures to prevent frost or reduce its severity include one or more of: *deploying powerful blowers to simulate wind, thereby preventing the formation of accumulations of cold air. There are variations on this theme. One variety is the wind machine, an engine-driven propeller mounted on a vertical pole that blows air almost horizontally. Wind machines were introduced as a method for frost protection in California during the 1920s, but they were not widely accepted until the 1940s and 1950s. Now, they are commonly used in many parts of the world. Another is the

selective inverted sink The selective inverted sink or SIS is a device used by farmers to protect plants from frost, developed by Uruguayan Rafael Guarga in the late 1990s. The sink is actually a large fan housed in a chimney-like structure, and works by defeating s ...

, a device which prevents frost by drawing cold air from the ground and blowing it up through a chimney. It was originally developed to prevent frost damage to

citrus ''Citrus'' is a genus of flowering plant, flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as Orange (fruit), oranges, Lemon, lemons, grapefruits, pomelos, and lim ...

fruits in

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

. In New Zealand,

helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

s are used in similar fashion, especially in the

vineyard A vineyard (; also ) is a plantation of grape-bearing vines, grown mainly for winemaking, but also raisins, table grapes and non-alcoholic grape juice. The science, practice and study of vineyard production is known as viticulture. Vineyards ...

regions such as

Marlborough Marlborough may refer to: Places United Kingdom * Marlborough, Wiltshire, England ** Marlborough College, public school * Marlborough School, Woodstock in Oxfordshire, England * The Marlborough Science Academy in Hertfordshire, England Austral ...

. By dragging down warmer air from the inversion layers, and preventing the ponding of colder air on the ground, the low-flying helicopters prevent damage to the fruit buds. As the operations are conducted at night, and have in the past involved up to 130 aircraft per night in one region, safety rules are strict.''Helicopters Fight Frost'' – ''Vector'',

Civil Aviation Authority of New Zealand The Civil Aviation Authority of New Zealand (CAA; Māori: ''Te Mana Rererangi Tūmatanui o Aotearoa'') is the government agency tasked with establishing civil aviation safety and security standards in New Zealand. The CAA also monitors adherence ...

, September/ October 2008, Page 8-9 Although not a dedicated method,

wind turbine A wind turbine is a device that converts the kinetic energy of wind into electrical energy. Hundreds of thousands of large turbines, in installations known as wind farms, now generate over 650 gigawatts of power, with 60 GW added each year. ...

s have similar (small) effect of vertically mixing air layers of different temperature.Turbines and turbulence
, ''

Nature (journal) ''Nature'' is a British weekly scientific journal founded and based in London, England. As a multidisciplinary publication, ''Nature'' features peer-reviewed research from a variety of academic disciplines, mainly in science and technology. ...

'', 468, 1001, 23 December 2010, DOI:10.1038/4681001a, published online 22 December 2010.Somnath Baidya Roy and Justin J. Traiteur
Impacts of wind farms on surface air temperatures
Proceedings of the National Academy of Sciences, Vol. 107, No. 42, October 19, 2010, p. 17,899.
, Science Daily. *For high-value crops, farmers may wrap trees and cover crops. *Heating to slow the drop in temperature is not practical except for high-value crops grown over small areas. *Production of smoke to reduce cooling by radiation *Spraying crops with a layer of water releases latent heat, preventing harmful freezing of the tissues of the plants that it coats. Such measures need to be applied with discretion, because they may do more harm than good; for example, spraying crops with water can cause damage if the plants become overburdened with ice. An effective, low cost method for small crop farms and plant nurseries, exploits the latent heat of freezing. A pulsed irrigation timer delivers water through existing overhead sprinklers at a low volumes to combat frosts down to . If the water freezes, it gives off its latent heat, preventing the temperature of the foliage from falling much below zero.

Frost-free areas

Frost-free areas are found mainly in the lowland tropics, where they cover almost all land except at

altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...

s above about near the equator and around in the semiarid areas in tropical regions. Some areas on the oceanic margins of the subtropics are also frost-free, as are highly oceanic areas near windward coasts. The most poleward frost-free areas are the lower altitudes of the

Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...

Île Amsterdam Île Amsterdam (), also known as Amsterdam Island and New Amsterdam (''Nouvelle-Amsterdam''), is an island of the French Southern and Antarctic Lands in the southern Indian Ocean that together with neighbouring Île Saint-Paul to the south for ...

Île Saint-Paul Île Saint-Paul (Saint Paul Island) is an island forming part of the French Southern and Antarctic Lands (''Terres australes et antarctiques françaises'', TAAF) in the Indian Ocean, with an area of . The island is located about south of the la ...

, and

Tristan da Cunha Tristan da Cunha (), colloquially Tristan, is a remote group of volcanic islands in the South Atlantic Ocean. It is the most remote inhabited archipelago in the world, lying approximately from Cape Town in South Africa, from Saint Helena ...

. In the

contiguous United States The contiguous United States (officially the conterminous United States) consists of the 48 adjoining U.S. states and the Federal District of the United States of America. The term excludes the only two non-contiguous states, Alaska and Hawaii ...

, southern Florida around

Miami Beach Miami Beach is a coastal resort city in Miami-Dade County, Florida. It was incorporated on March 26, 1915. The municipality is located on natural and man-made barrier islands between the Atlantic Ocean and Biscayne Bay, the latter of which sep ...

and the

Florida Keys The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami, and e ...

are the only reliably frost-free areas, as well as the Channel Islands off the coast of

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. The

hardiness zone A hardiness zone is a geographic area defined as having a certain average annual minimum temperature, a factor relevant to the survival of many plants. In some systems other statistics are included in the calculations. The original and most wide ...

s in these regions are 11a and 11b.

Personifications

Frost is personified in Russian culture as

Ded Moroz Ded Moroz (russian: Дед Мороз, ; Russian diminutive: russian: Дедушка Мороз, Dedushka Moroz, label=none; sk, Dedo Mráz; pl, Dziadek Mróz) or Morozko (russian: Морозко) is a legendary figure similar to Saint Nich ...

Indigenous peoples of Russia Lists of indigenous peoples of Russia cover the indigenous ethnic groups in Russia other than Russians. As of 2010 these constituted about 20% of the population. The period lists are organized by the official classifications based on the number o ...

such as the

Mordvins The Mordvins (also Unified Mordvin people, Mordvinians, Mordovians; russian: мордва, Mordva, Mordvins (no equivalents in Moksha and Erzya)) is an obsolete but official term used in the Russian Federation to refer both to Erzyas and Moksh ...

have their own traditions of frost deities. English folklore tradition holds that

Jack Frost Jack Frost is a personification of frost, ice, snow, sleet, winter, and freezing cold. He is a variant of Old Man Winter who is held responsible for frosty weather, nipping the fingers and toes in such weather, coloring the foliage in autumn, ...

, an elfish creature, is responsible for feathery patterns of frost found on windows on cold mornings.

Gallery

File:Frost on a nettle, Netherlands.jpg, Frost on a nettle File:Fern Frost.JPG, Fern frost on a window File:Dülmen, Hausdülmen, Distel -- 2021 -- 5079.jpg, Frost on a thistle in Hausdülmen,

North Rhine-Westphalia North Rhine-Westphalia (german: Nordrhein-Westfalen, ; li, Noordrien-Wesfale ; nds, Noordrhien-Westfalen; ksh, Noodrhing-Wäßßfaale), commonly shortened to NRW (), is a States of Germany, state (''Land'') in Western Germany. With more tha ...

, Germany File:Window-Frost.jpg, Window frost File:Frost on leaves.jpg, Frost on plant leaves in the

Himalayas The Himalayas, or Himalaya (; ; ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the planet's highest peaks, including the very highest, Mount Everest. Over 100 ...

File:Hoar Frost.JPG, Surface hoar in

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

File:Hoar frost on a snow field.jpg, Hoar frost in

Julian Alps The Julian Alps ( sl, Julijske Alpe, it, Alpi Giulie, , ) are a mountain range of the Southern Limestone Alps that stretch from northeastern Italy to Slovenia, where they rise to 2,864 m at Mount Triglav, the highest peak in Slovenia. A large pa ...

File:Frost on Birch Tree in Stockholm 20180110.jpg, Frost on birch tree in

Stockholm Stockholm () is the Capital city, capital and List of urban areas in Sweden by population, largest city of Sweden as well as the List of urban areas in the Nordic countries, largest urban area in Scandinavia. Approximately 980,000 people liv ...

File:Frost in Ranu Pani on 4 August 2018 by Susanto Tan 6.jpg, Frost on grass in Ranu Pani,

East Java East Java ( id, Jawa Timur) is a Provinces of Indonesia, province of Indonesia located in the easternmost hemisphere of Java island. It has a land border only with the province of Central Java to the west; the Java Sea and the Indian Ocean bord ...

, Indonesia File:Frost on birch tree.jpg, Frost on birch stem in

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

File:Sydneyfrost.jpg, Frost on grass in

Sydney Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mountain ...

File:Leaf with frost.jpg, An oak leaf with frost in

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

References

External links

Guide to FrostHow much do you know about frost?
– ''BBC''
American Meteorological Society, ''Glossary of Meteorology'' – Hoarfrost
* {{Authority control Frost and rime Psychrometrics Water ice