All schools in the Mehlville School District and Lindbergh Schools will close Wednesday due to the wind chill warning issued by the National Weather Service, which projects record lows.

Lindbergh canceled all before, after school and evening activities, and officials said they expect for school to be in session Thursday.

Mehlville said that students should wait to hear from their activities staff or coaches to find out if after-school events will be canceled Wednesday.

The National Weather Service is projecting dangerously cold wind chills through noon Thursday, sinking to unprecedented levels in St. Louis.

It’s part of a broader effect on the Midwest and the East Coast from the polar vortex.

The warning is in effect from Tuesday evening until Thursday morning.

“The dangerously cold wind chills could cause frostbite on exposed skin in as little as 10 minutes,” according to the NWS alert.

Affected areas include St. Louis County and St. Louis city, St. Charles County, Jefferson County and Lincoln County, along with other Missouri counties: Moniteau, Cole, Shelby, Audrain, Brown, Washington, Calhoun, Pike, Warren, Gasconade, Callaway, Adams, Osage, Crawford, Boone, Lewis and Ralls.

The warning also includes Illinois counties: St. Clair, Madison, Bond, Monroe, Montgomery, Clinton, Greene, Marion, Macoupin, Jersey and Fayette counties.