A quick meteorology lesson...

Right now the southern portion of NJ is seeing the coldest temperatures. Why? Clear skies there have allowed for heat to escape while up north the cloudy conditions act like a blanket trapping the warmer air. Some places in South Jersey saw 40 degrees for highs and are currently at 23 degrees while Netcong saw a high of 30 and is currently at 28 during the same time frame. Now that's why I love meteorology!