On Thursday at 1:08 a.m. the National Weather Service released a cold weather advisory valid from 7 p.m. until Friday 10 a.m. for Jefferson and Lewis counties. The weather service adds, “Bitterly cold wind chills as low as 29 degrees below zero expected.”“Bitterly cold wind chills as low as 29 below zero will cause frostbite on exposed skin in as little as 15 minutes. Frostbite can occur in 30 minutes or less with apparent temperatures of 15 below zero or colder.”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.