Annual Overview

Following a cooler-than-normal November, it was back to the mild side in December, the ninth such month in 2021. However, much like November, the last month of 2021 was a top 10 dry one. An annual recap follows the December report where more will be said regarding annual temperature and precipitation.

Statewide precipitation in December was 1.29”. This is 2.98” below the 1991–2020 normal and ranks as the 6th driest since records commenced in 1895. It was the driest December since 1989, which happened to be the coldest December on record. The west-central area received the most precipitation, exceeding 1.80” in some locations, but this was still well below normal. The far south was driest, most places receiving less than an inch. The northern division averaged 1.46”, which is 2.79” below normal and ranked 10th driest. The southern division came in with 1.20”, which is 3.08” below normal and ranks 5th driest. The coastal division with 1.09” was 3.27” below normal and ranked 4th driest.

There were multiple faces to December weather around the Garden State. Regionally, the north received above-average snowfall, several episodes of freezing rain, and over two weeks of snow cover, particularly at higher elevations. Central and southern areas saw less snow than average and temperatures a little milder than normal compared to up north. There was also a notable difference between the first and second halves of the month, with the first being stormy and the second having just one storm.

Despite a wintry start to the month, the statewide average temperature of 36.3° was 1.1° above the 1981–2010 normal and ranks as the 29th mildest since 1895 (tied with 2016). The north portion of the state averaged 33.1° (+0.4°), the south 38.2° (+1.6°), and the coast 39.4° (+1.7°). Despite a rather dry second half, the 5.56” of rain and melted snowfall averaged across the state was 1.71” above average, ranking as the 19th wettest (tied with 2012). The coast was wettest, averaging 6.09” (+2.33”), followed by the south with 5.60” (+1.81”), and then the north with 5.44” (+1.49”). Snowfall averaged 3.2”, which was 1.6” below average. The north came in with 8.0”, or 1.4” more than average, while the central area had 3.4” (-2.0”) and the south 0.5” (-3.1”).

New Jersey residents will long remember the last month of 2015 as one where the grass remained green, weeds grew, and a few blossoms were seen on trees and shrubs. In fact, with an average temperature of 47.8°, it was the mildest December on record by a wide margin based on records dating back to 1895. Five of the 6 mildest Decembers have occurred since 2001. The anomaly of +12.2° exceeds the +11.0° value in January 1932 as the largest positive anomaly of any month on record. The 5.6° difference between this December's average and the second mildest in 2006 is by far the largest difference between first and second warmest values of any month. The second largest margin is 2.3° between October 2007 and 1971. With 121 years of records, the difference between one ranking and the next is often a tenth to a few tenths of a degree.

December precipitation averaged 4.91" statewide. This is 1.00" above normal and ranks as 27th wettest on record. Snow and sleet fell on one occasion, with light accumulations reported in the north. The statewide 0.1" snowfall average was 5.4" below normal. While certainly on the light side, this is not too out of the ordinary. Seven Decembers since 1895 have failed to see any snow accumulate, and 12 prior Decembers had a statewide average somewhere between 0.1" to 0.5".