A "pneumonia front" will hit the Chicago area Tuesday, sending temperatures plummeting in a matter of minutes, but what is it and when will it hit?
NBC 5 Storm Team meteorologist Brant Miller said the term typically refers to a "backdoor cold front" influenced by Lake Michigan, in which the front comes from the northeast rather than the north and west.
Cold fronts that race south over Lake Michigan in the early spring and summer can cause temperatures to drop dramatically. According to experts it is essentially a more-intense version of the lakefront breezes that typically cause lower temperatures near the lake during the summer months.
According to Weather Underground, the term “pneumonia front” was first coined by the National Weather Service’s Milwaukee office in the 1960’s. The NWS Chicago office notes that the differences in air density between the cold front and the air ahead of it make the front race more quickly, as does the lower friction caused by the front passing over water rather than land.
Pneumonia fronts tend to occur during the spring when the lake temperatures are colder.
But Miller noted the name can be misleading.
"Pneumonia is really viral or bacterial," he said. "The temperature really doesn't have anything to do with that."
Local
No matter the name, the front will cause temperatures to drop more than 20 degrees in a matter of minutes Tuesday.
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.
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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 during the day, but as the front passes through, temperatures will drop into the mid-50s in areas east of Interstate 355, according to officials.
The NBC 5 Storm Team said the rapid drop will likely take place after 5 p.m.
Residents are advised to bring extra layers of clothing if they are out and about Tuesday evening.
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.
The temperature drop will last through Wednesday, with highs in the upper-50s near the lakefront, but those highs should rebound into Thursday, with highs reaching to nearly 70 degrees.
