On Friday at 12:06 a.m. the National Weather Service released a cold weather advisory valid from 7 p.m. until Saturday 11 a.m. for Northern Erie and Southern Erie as well as Crawford County. The weather service says, "Very cold wind chills as low as 21 degrees below expected." "The cold wind chills as low as 20 below zero could cause frostbite on exposed skin in as little as 30 minutes," describes the weather service. 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.