A so-called “pneumonia front” is going to sweep off of Lake Michigan on Tuesday afternoon, dropping temperatures more than 20 degrees within a matter of minutes.
According to the National Weather Service, the cold front will impact areas near the lake beginning late Tuesday afternoon and into the early evening hours.
Temperatures are expected to reach into the low-80s across much of the area, but as the front passes through, temperatures will drop into the mid-50s in areas east of Interstate 355, with many locations seeing temps plunge more than 20 degrees within a matter of minutes, according to officials.
Residents are advised to bring extra layers of clothing if they are out and about Tuesday evening thanks to the rapidly-dwindling temperatures.
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Areas to the west of Interstate 355 will also see temperatures decrease during the late afternoon and into the evening, though the front won’t be quite so impactful in those locations.
According to Weather Underground, the term “pneumonia front” was first coined by the National Weather Service’s Milwaukee office in the 1960’s. Cold fronts that race south over Lake Michigan in the early spring and summer can cause temperatures to drop dramatically, and according to experts is essentially a more-intense version of the lakefront breezes that typically cause lower temperatures near the lake during the summer months.
According to the National Weather Service’s Chicago office, the differences in air density between the cold front and the air ahead of it makes the front race more quickly, as does the lower friction caused by the front passing over water rather than land.
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Pneumonia fronts tend to occur during the spring when the lake temperatures are colder.
This front will not only impact parts of northeastern Illinois, including in Lake and Cook counties, but also parts of Wisconsin, including the Milwaukee area.
The temperature drop will last through Wednesday, with highs in the upper-50s, but those highs should rebound into Thursday, with highs reaching to nearly 70 degrees.
