On Thursday at 2:17 p.m. EST a cold weather advisory was released by the National Weather Service valid for Friday between midnight EST and 10 a.m. EST for Midland, Bay, Huron, Saginaw, Tuscola and Sanilac counties. The weather service describes, "Very cold wind chills as low as 15 to 20 degrees below zero expected." Understanding cold weather alertsCold weather advisory: Be Aware. A cold weather advisory is issued when seasonably cold air temperatures or wind chill values, but not extremely cold values, are expected or occurring. An extreme cold warning is issued when dangerously cold air temperatures or wind chill values are expected or occurring.