* WHAT...For the Extreme Cold Warning, dangerously cold wind chills as low as 21 below. For the Cold Weather Advisory, very cold wind chills as low as 14 below expected. * WHERE...In New Jersey, Eastern Bergen, Eastern Passaic, and Western Bergen Counties. In New York, Northern Westchester, Putnam, Rockland, and Southern Westchester Counties. * WHEN...For the Extreme Cold Warning, until 1 PM EST this afternoon. For the Cold Weather Advisory, from 1 PM this afternoon to 10 AM EST Monday. * IMPACTS...The cold wind chills could cause frostbite on exposed skin in as little as 30 minutes.