The term Pneumonia front, first coined by the National Weather Service in Milwaukee in the 1960s, is used to describe a rare meteorological phenomenon observed on the western shoreline of

Lake Michigan Lake Michigan is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and the third-largest by surface area (), after Lake Superior and Lake Huron. To the east, its basin is conjoined with that o ...

during Spring and early Summer. These fronts are defined as lake-modified synoptic scale cold fronts that result in one-hour temperature drops of 16 °F (8.9 °C) or greater. They do not necessarily have to be synoptic, or large scale, cold fronts. Pneumonia fronts are most common between the months of April to July when the temperature difference between the cold lake waters and the warmer air over land can be as much as . Under weak prevailing winds, a density current can often develop in the form of a lake breeze that moves from that water to the adjacent shoreline and several miles inland. This "lake-breeze cold front" can drop temperature in places like Chicago, Milwaukee,

Benton Harbor Benton Harbor is a city in Berrien County in the U.S. state of Michigan. It is 46 miles southwest of Kalamazoo and 71 miles southwest of Grand Rapids. According to the 2020 census, its population was 9,103. It is the smaller, by population, of ...

, and Green Bay significantly as they cross the area. There has been many times during spring games at Wrigley Field where people, who may have traveled far to the lakeshore of Lake Michigan from an inland location to watch an afternoon game, only to feel the effects of the "pneumonia front" as that cold blast of air comes through. The following are documented occurrences of a lake modified synoptic scale cold front or a "pneumonia front".

References

{{Reflist

External links

"Synoptic and Local Controls of the Lake Michigan Pneumonia Front", C. Behnke, M.S. Thesis, University of Wisconsin - Milwaukee (2005)CIMSS Satellite Blog
Anomalous weather Weather fronts Lake Michigan Weather and health