The cold and wind have returned to Sioux Falls. The National Weather Service has issued a Wind Chill Warning for Thursday. The warning includes Sioux Falls, Mitchell, Bookings and Worthington. A Wind Chill Advisory is in effect for areas south of Sioux Falls.The cold  caused Sioux Falls Schools to close Thursday. Dangerous wind chills of 20 to 40 bellow zero are possible. From the NWS:

A WIND CHILL WARNING MEANS THE COMBINATION OF VERY COLD AIR AND STRONG WINDS WILL CREATE DANGEROUSLY LOW WIND CHILL VALUES. THIS WILL RESULT IN FROST BITE AND LEAD TO HYPOTHERMIA OR DEATH IF PRECAUTIONS ARE NOT TAKEN.