Monthly Summaries

Weather often varies from week-to-week and even day-to-day during the spring transition season. Such was certainly the case in spring 2021, as will be recapped later in this report. However, when it came to such “weather indecision,” May 2021 took the cake. Starting off somewhat damp with seasonable temperatures, a prolonged period of exceedingly dry weather ensued, first accompanied by cooler-than-normal temperatures and frosty mornings, and later by summer-like heat. As several wildfires broke out and soil moisture vanished, concerns of early-summer drought arose. Then along came one of the coolest Memorial Day weekends on record, accompanied by more than an average May’s worth of rain in some locations. This led to frequent decision making amongst farmers, gardeners, water resource managers, utility companies and customers, and day trippers. All were left wondering what might come next! Cicadas perhaps?

With the thermometer up and down throughout May, the statewide average temperature of 61.0° was just 0.2° below the new 1991–2020 normal. This ranked as the 47th mildest May since 1895. The average maximum of 73.0° was 0.7° above normal, while the 49.0° average minimum was 1.2° below normal. This is illustrative of a month that had many clear days and cool nights with low humidity. Despite dry conditions for most of the month, monthly precipitation came in close to normal, averaging 3.95” across NJ. This is 0.20” above normal, ranking 48th wettest of the past 127 years. Far south and west central areas were driest, while the central coast and northeast saw the most rain. Unlike last May, no snow was observed.

With March being a transitional weather and climate month, there are often pronounced differences in conditions from one day or week to the next. The third month of 2021 did not disappoint in several such respects. Swings in barometric pressure as storms and high pressure systems swung through the Northeast led to 16 days with one or more Rutgers NJ Weather Network stations gusting to 40 mph or higher, with 11 of those days exceeding 50 mph. Maximum temperatures exceeded 65° on 12 days (two days had record highs in some locations), while minimum temperatures fell below 19° on 13 days. Walpack, situated in a Sussex County valley, recorded the state’s lowest (21°) and highest (67°) temperatures on a single day (22nd) and just missed this again on the 30th. There was a two-week interval with virtually no precipitation, culminating in several wildfires on the 14th, yet five events occurred where rain accumulated to 0.98” in one or more locations. Finally, a record of sorts was tied as the statewide average snowfall totaled 0.0”, something observed eight other Marches in the past 127 years. The past two Marches are the only ones with back-to-back zero totals.

Statewide precipitation averaged 4.03”, which is 0.18” below the 1991–2020 average*. This made for the 58th wettest (70th driest) since 1895. Northern NJ was driest, coming in at 3.28” (-0.73, 48th driest), the south averaged 4.47” (+0.15”, 42nd wettest), and the coast 4.68” (+0.26”, 38th wettest). The southeast saw the most rain and northeast and central regions the least (Figure 1).

March temperature average 43.9°, which is 2.9° above the 1991–2020 average and the 14th mildest on record. The average high was 54.7° (+3.8°, 13th mildest) and average low was 33.0° (+1.8°, 19th mildest). The north averaged 41.2° (+2.4°, 19th mildest), south 45.6° (+3.2°, 13th mildest), and the coast 45.1° (+2.9°, 13th mildest).

The first month of 2021 lacked major storms, whether wet or white, and temperatures rarely were either quite mild or very cold. Thus the title of this report. Yes, the last day of the month turned snowy, the harbinger of anything but a boring start to February, but that’s to be covered next month. The January statewide average temperature was 33.7°. This was 3.0° above the 1981–2010 normal and ranks as the 26th mildest January in the past 127 years. The average high was 41.1°, which is 1.8° above normal and ranks 34th mildest, while the average low of 26.3° was 4.2° above normal, ranking 20th mildest.

January precipitation (rain and melted snow) averaged 1.99” across the state, which is 1.41” below normal and ranks 13th driest since 1895. The north averaged 1.93” (-1.48”, 18th driest), the south 2.02” (-1.37”, 13th driest), and the coast 2.19” (-1.25”, 17th driest). Generally, the eastern half of the state was wetter (particularly the northeast) than the west.

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.