* WHAT...Very cold wind chills as low as 20 to 25 below expected.

* WHERE...Boone, De Kalb, Ogle, Winnebago, Kane, and McHenry Counties.

* WHEN...From 3 AM Sunday to noon CST Monday.

* IMPACTS...The dangerously cold wind chills as low as 20 to 25 below zero could cause frostbite on exposed skin in as little as 30 minutes.

* ADDITIONAL DETAILS...Wind chills will drop to around 20 below zero Sunday morning, recover slightly Sunday afternoon, and then fall to 20 to 25 below zero Sunday night into Monday morning. After some recovery Monday afternoon, another round of dangerously cold wind chills is expected Monday night into Tuesday morning.