* WHAT...Very cold wind chills as low as 25 to 30 below expected.

* WHERE...Portions of north central and northeast Illinois and northwest Indiana.

* WHEN...From 9 PM this evening to noon CST Tuesday.

* IMPACTS...The dangerously cold wind chills as low as 25 to 30 below zero could cause frostbite on exposed skin in as little as 30 minutes.