Fall

Foggy mornings, clear days, four modest rain events, and most locations yet registering a fall freeze. This all speaks to a rather quiet weather October, thus the title of this report. The rather dry conditions resulted in statewide monthly precipitation averaging just 2.16”. This was 2.03” below normal and ranked as the 32nd driest October since records commenced in 1895. Under an inch fell in the southwest, while only the northeast and northern coast saw totals close to or above normal. The northern climate division averaged 3.06” (-1.39”, 56th driest), southern division 1.57” (-2.46”, 17th driest), and coastal division 2.00” (-2.09”, 30th driest).

As a result of above-normal temperatures to begin and end the month, the statewide average temperature of 58.2° was 2.8° above normal, ranking 9th warmest (tied with 2019). Every other October since 2017 sits in the top 10. The northern division averaged 56.4° (+3.1°, 9th warmest), southern 59.2° (+2.7°, 12th warmest), and coastal 60.2° (+2.6°, 11th warmest).

Last month’s report spoke of how “classic” the weather was during October. November’s weather could be classified as being anything but such. The month began with perhaps the warmest first ten days of November on record in the Garden State, an interval that ranked up there with early November 2020. Then came winter-like temperatures for about ten days leading up to Thanksgiving before the month ended on a closer-to-normal note. There were only two mid-month events that brought more than an inch of rain to parts of the state, one associated with the remnants of a late-season hurricane that struck Florida. Portions of central and northern NJ saw the first snowflakes of the season during the cold spell, though aside from some minor accumulations at higher elevations, mostly traces were observed.

With the ups and downs of temperature, November came out averaging 47.5° for the state as a whole. This is 2.4° above the 1991–2020 normal and ties as the 15th mildest eleventh month on record. Ten of the twenty mildest Novembers since 1895 have occurred since 2001. The statewide average high temperature of 58.1° was 3.4° above normal, ranking 10th mildest. The average low of 36.9° was 1.4° above normal, ranking 20th mildest. North Jersey averaged 45.2° (+2.1, 15th mildest), south Jersey 48.7° (+2.4°, 17th mildest), and the Jersey coast 50.0° (+2.7°, 13th mildest).

Statewide precipitation averaged 3.08”, which is 0.28” below normal and ranks as the 63rd driest (66th wettest) on record. The north averaged 2.98” (-0.28”, 63rd driest), south 3.14” (-0.15”, 71st driest), and coast 3.14” (-0.20”, 68th driest). As the monthly map shows, central and northern coastal areas were wettest, while the driest areas were scattered in the far south, central, and north. It must be noted that the rain falling during the second half of the 30th is not included in the monthly totals for the state, regions, or individual stations presented later in the report. By convention, the reporting day for most National Weather Service (NWS) Cooperative and Community Collaborative Rain, Hail, and Snow Network (CoCoRaHS) stations used in this report ends at morning observation time on the last day of the month. Totals from the afternoon of the 30th, to be included in December totals, ranged as high as about an inch, though mainly 0.25”–1.00”.

Following a hot and dry summer, the questions of the day in September were when the temperature would begin to cool and would more abundant rainfall arrive. Signs of a rainfall resurgence were mixed, with drought conditions diminishing in spots but worsening in others. The temperature answer came in almost a flash on the 22nd (the first day of astronomical fall!) when a powerful cold front sent the thermometer quickly downward with an early-fall-like pattern arriving and remaining through month’s end.

September temperatures averaged 67.8° across NJ. This is 0.9° above the 1991–2020 normal and ties as the 22nd mildest September since statewide records commenced in 1895. The average high temperature was 78.2°, which is 1.0° above normal and tied for 23rd warmest. The average low was 57.3°, 0.7° above normal and ranking 23rd warmest. North Jersey came in at 65.7° (+0.8°, tied for 23rd warmest), the south 69.0° (+0.9°, tied for 21st warmest), and the coast 69.7° (+1.0°, 15th warmest).

NJ precipitation averaged 3.16” for September, which is 1.00” below normal and ranks as the 57th driest of the last 128 years. The north was wettest at 3.64”. This is 0.82” below normal, though ranks as just the 67th driest. The south came in with 2.86” (-1.13”, 51st driest) and the coast 2.98” (-0.91”, 57th driest).

October was the second mildest on record in the Garden State since records commenced in 1895. This follows on the heels of the 11th warmest September, leaving most residents wondering when cool weather would arrive and leaves would turn and fall. For the first time since at least 1900, not a single weather observing station in New Jersey recorded a freezing low temperature on any day in either September or, as is climatologically most common, October. All of this resulted in a leaf season that was delayed by one to two weeks.

The statewide average October temperature of 61.1° was 5.7° above the 1991–2020 normal, a mark only surpassed in 2007. The average daily maximum of 70.1° (+4.3°) ranked 5th mildest (tied with 1920), and the average minimum of 52.0° (+7.1°) tied with 2007 as the mildest. These temperatures are close to what Norfolk, Virginia, normally experiences in October. In fact, despite the mean temperature normally declining 11.5° from September to October, this year’s mean was warmer than four previous Septembers since 1895 and the minimum was milder than 14 earlier Septembers. The state’s three climate divisions all ranked second mildest, with the north at 59.0° (+5.7°), south 62.3° (+5.8°), and coastal 63.2° (+5.6°).

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.