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The statewide average temperature during this last month of 2020 averaged 37.0°. This was 1.8° above the 1981–2010 normal and ranks as the 22nd mildest December in the 126-year record that dates back to 1895. Northern and southern portions of NJ had similar departures and rankings.

December precipitation (rain and the liquid equivalent of snow and sleet) averaged 6.24”. This includes rain measured at National Weather Service Cooperative Observing stations on the morning of December 1st but does not include rain measured at these stations for the 24 hours ending on the morning of January 1st. See an explanation of the November 30th–December 1st measurement in the November report. The monthly value is 2.39” above average and ranks as the 11th highest December precipitation total on record. North Jersey averaged 6.73”, which is 2.78” above average and ranks 7th wettest. The south came in at 5.89”, which is 2.10” above average and ranks 17th wettest. The coast averaged 6.43”, which is 2.67” above average and ranks 11th wettest.

November 2020 enters the New Jersey climate record book as the third warmest (tied with 2009). The statewide mean of 49.2° was 4.0° above the 1981–2010 normal. This month joins six Novembers from this century among the seven warmest of the past 126 years. Six of the past 12 months have ranked in the top nine for warmth. Of the first 11 months of 2020, only April and May averaged below normal. The average temperature for the first 11 months is 57.1°. This is 2.7° above normal and ranks as the second warmest such interval. Only 2012 was warmer, with both years likely to retain this ranking for the calendar year unless an extremely cold or warm December occurs, which, as this report is written, appears unlikely.

Statewide precipitation total for November was 3.91”. This was 0.30” above the 1981–2010 normal and ranks as the 43rd wettest of the past 126 years. The southern half of the state was on the wetter side of normal while the north on the dry side. This was seen in the divisional numbers that had the south come in with 4.43”, which is 0.98” above average 33rd wettest, while the north averaged 3.09”, which is 0.77” below average and ranks 78th wettest (49th driest).

September 2020 was a month of widely-varying temperatures, several episodes of heavy precipitation, and an extended dry spell. Put it all together and conditions averaged quite close to normal. The statewide monthly average temperature of 66.8° was 1.0° above the 1981–2010 mean. While it was the seventh month of 2020 to average above normal, it was the first of these not to rank in the top 10 for warmth. Rather, it ranked 33rd warmest of the past 126 Septembers. Divisional departures from normal ranged from +0.7° in the north to +1.5° along the coast. The statewide average maximum temperature was 76.6°, which is 0.3° above normal and ranks 47th warmest. The average minimum of 56.9° was 1.6° on the warm side and ranked 24th mildest. High temperatures were likely reduced by several degrees during a mid-month period when a veil of smoke from western US forest fires blanketed the sky at an altitude of about 15,000 feet when skies otherwise would have been blue, especially on the 15th–16th. It is uncertain if this kept minimum temperatures somewhat warmer than they would otherwise have been. A cold front moved through from the northwest on the 18th, clearing the skies and sending temperatures plummeting. What followed was a four-day spell of temperatures that were well below average, including four nights with below-freezing temperatures at three to four Rutgers NJ Weather Network sites. While freezes resulting from cold air draining into valleys in some northern locations are not unprecedented before the end of astronomical summer, it is highly unusual for the cold to persist over four consecutive nights.

July 2020 was the hottest month on record for the Garden State since records commenced in 1895. The statewide average temperature of 78.8° was 4.2° above the 1981–2010 normal. This reading surpasses by 0.4° the previous record held jointly by 1955, 1999, and 2011. The next ten warmest months have occurred in July, with the warmest August averaging 76.8° in 2016, which is tied with July 1994 as the 11th warmest month on record. The average 88.9° maximum this past July was 5th warmest, the warmest occurring in 1999. The average minimum of 68.8° ranked second, trailing just 2013. The southern and coastal climate divisions had their warmest month on record while the northern division ranked second.

The statewide average precipitation this July was 6.79”. This is 2.22” above the 1981–2010 normal and ranks as the 15th wettest July on record. Looking at the state in quarters from north to south, the northernmost was driest, particularly the northwest. Next came a wet sector, followed by a more average one, with the southernmost quarter the wettest. Few locations received less than 4 inches, while scattered totals of more than 10 inches were found in the two wettest quarters.

In recent years, many a comment has been heard that New Jersey just does not have a spring season any more. We go right from winter to summer weather, people say. The same cannot be said for spring 2020. A seasonal summary follows at the end of this report and the individual March and April reports can be found on the state climate office website. To begin here, the talk will be of May, a month that produced both less rain and cooler temperatures than normal and included an unusual appearance of snow.

The statewide average temperature of 58.9° was 1.7° below the 1981–2010 normal. This ranked as the 40th coolest May since records commenced in 1895. April and May marked the first time since December 2017–January 2018 that consecutive months had below-average temperatures. Statewide, May precipitation averaged 2.50”. This was 1.49” below normal and ranked as the 29th driest on record.