The National Weather Service released a cold weather advisory at 12:50 p.m. EST on Wednesday valid from 10 p.m. EST until Thursday 10 a.m. EST for Chippewa and Mackinac counties. 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. An extreme cold watch is issued when dangerously cold air temperatures or wind chill values are possible.