The bitter cold air mass expected over Wisconsin is the worst in about 18 years.
According to the National Weather Service, wind chills are expected to drop to 20 to 25 below late Saturday and Sunday in south central Wisconsin and then plummet to 40 to 55 below throughout the state by Monday morning and again Tuesday morning.
A wind chill warning is in effect from 6 p.m. Sunday through Tuesday at noon.
The last time it was this cold was in February 1996.
The weather service also says a low pressure system has shifted and now threatens to bring about 3 to 5 inches of snow to the far southeast corner of Wisconsin on Sunday.