Monthly Summaries

It was a wet December, of this there is no doubt. In fact, it was New Jersey’s wettest 12th month on record, dating back to 1895. On multiple occasions, rainfall arrived in multiple-inch increments, leading to episodes of minor to major stream and river flooding. Though hardly maliciously, Mother Nature certainly left the tap flowing far too long and often!

Monthly rainfall (with a little melted snowfall added to the mix in some locations) averaged 8.20” across the state (Figure 1). This was 3.93” above the 1991–2020 normal and was 0.33” above the previous wettest December in 1996 (Table 1). Precipitation averaged 8.51” (+4.26”, 3rd wettest) in the northern climate division (Hunterdon-Somerset-Union northward), 8.02” (+3.74”, 2nd wettest) over the southern division (Mercer-Middlesex-Monmouth mostly southward), and 7.88” (+3.52”, 2nd wettest) in the coastal division (generally east of the Garden State Parkway from Monmouth to Cape May).

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).

It is not as if August 2023 was devoid of strong thunderstorms that produced locally heavy rain and three minor tornadoes. There were also some hot and humid days and even a few days with smoke high aloft, a rather persistent feature of this summer’s weather (more on this in earlier June and July recaps and the summer summary later in this report). However, with temperatures a bit below normal and statewide rainfall leaning that way too, it just was not a particularly notable August in the weather/climate department. Mind you, most folks hardly complained of 90° maximum temperatures being rather scarce, there being no soaking tropical system, and, for the most part, fine weather for outdoor activities.

Statewide, the average temperature of 72.9° was 0.7° below the 1991–2020 normal. This ranked as the 48th warmest August of the past 129, but the coolest since 2017. Three of the past four months have been below normal, something not accomplished since January, March, and April 2018. The average high of 82.4° was 1.4° below normal, ranking 60th warmest. The low of 63.4° was 0.1° above normal, raking 31st warmest. The northern climate division averaged 70.7° (-1.2°, 53rd warmest), the southern division 74.2° (-0.4°, 46th warmest), and coastal division 74.5° (-0.2°, 38th warmest).

Precipitation averaged 4.03” across NJ, which is 0.54” below normal and ranks as 61st driest (68th wettest) since 1895. There was a north/south difference in rainfall, with the north averaging 5.02” (+0.46”, 41st wettest/89th driest), the south 3.45” (-1.12”, 49th driest/81st wettest), and coastal NJ 3.14” (-1.46”, 42nd driest/88th wettest).

There is rarely a month in New Jersey where something interesting, exciting, and different than normal doesn’t occur in the weather and climate department. However, not often do you find a month like this past June where one is left with their head spinning as smoke from near and distant wildfires darkened the sky, creating exceptionally unhealthy air quality, where growing drought concerns were quieted in most locations by late-month downpours, where two tornadoes touched down, and with temperatures averaging cooler than normal for the second consecutive month. Strange, indeed.

June temperatures across the state averaged 67.8°. This was 2.5° below the 1991–2020 mean and tied as the 36th coolest June since 1895. The average daily maximum temperature of 79.0° was 2.0° below normal and ranks 40th coolest. The daily minimum averaged 56.6°, 3.0° below normal and was 35th coolest. The northern NJ climate division averaged 66.1° (-2.5°, 33rd coolest), the southern division averaged 68.9° (-2.5°, 36th coolest), and the coastal division averaged 68.2° (-2.3°, 45th coolest). Both May and June averaged below normal, the first such back-to-back occurrence in NJ since April and May 2020.

NJ June precipitation averaged 3.87”. This was 0.43” below normal, however, it ranks as the 53rd wettest of the past 129 years (or 77th driest) due to the skewed nature of the distribution of monthly precipitation over this period. The north averaged 5.13” (+0.52”, 29th wettest [101st driest]), the south 3.19” (-0.95”, 51st driest [79th wettest]), and the coast 2.20” (-1.65”, 28th driest [102nd wettest]).

What can you say about a month that began with a swarm of tornadoes, finished with flooding rain, and in between, featured record heat, wildfires, and increasing drought concerns? Best to say that it was an odd one! Fitting this theme, the statewide average temperature of 55.4° was 3.9° above the 1991–2020 normal. This ranks as the third warmest April on record (since 1895) only behind 2017 and 2010 for top honors. April was the fifth month of the past ten ranking in the top 10, joining July (#7), August (#1), January (#1), and February (#5). The first four months of 2023 come in as the warmest start of the year on record with an average of 44.4°. This exceeds the previous record of 44.2° in 2012, with seven of the 10 warmest January–April periods (1895–present) occurring since 2002. The average April maximum temperature across NJ was 67.4° (+4.7°, 3rd warmest) and the average minimum was 43.4° (+3.1°, 5th warmest). Northern counties averaged 53.5° in April (+3.6°, 5th warmest), southern counties 56.6° (+4.0, 2nd warmest), and the coastal zone 55.8° (+4.1°, 2nd warmest).

April precipitation averaged 5.84” across New Jersey. This was 2.14” above normal, ranking as the 10th wettest on record. It was the wettest April since 2007 and second wettest since 1983. All but scattered areas in the northwest received above-normal precipitation, the greatest amounts falling near the Atlantic and Delaware Bay coasts. Northern counties averaged 5.55” (+1.65”, 26th wettest), southern counties 6.04” (+2.49”, 7th wettest), and the coastal zone 5.94” (+2.39”, 10th wettest). It is important to note that these totals and those for individual stations in the next section, do not include heavy rain that fell after standard early morning observation times at CoCoRaHS and National Weather Service Cooperative stations on April 30th. These rains were reported in morning observations on May 1st, thus will be included in May totals.