On Thursday at 12:51 a.m. the National Weather Service issued a cold weather advisory valid between 1 a.m. and 10 a.m. for Putnam, Rockland and Westchester 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. Extreme cold warning: Take Action! An extreme cold warning is issued when dangerously cold air temperatures or wind chill values are expected or occurring.