Summer

August joined the chorus of much warmer-than-normal months experienced throughout most of 2020 to date across the Garden State. Six of the eight months have ranked among the top 10 warmest for the 126 years beginning in 1895. Only April and May are outliers and, in fact, each of them had below-average temperatures. With a mean of 75.5°, August tied with 2001 and 1955 as the 6th warmest. This is 2.5° above the 1981–2010 mean. Eleven of the warmest 17 Augusts have occurred since 2001. The mean maximum of 84.8° tied for 19th warmest at 1.5° above normal, while the mean minimum of 66.1° was 3.4° above normal and ranked 4th warmest.

Statewide precipitation averaged 6.04”. This is 1.94” above normal and ranks as the 26th wettest August on record. Above-average totals occurred in northern (6.02”), southern (6.10”), and coastal (5.50”) climate divisions. The southern division (Mercer-Middlesex-Monmouth counties and south, except a narrow coastal division) saw a range from the driest area in Monmouth and parts of Mercer counties and a very wet area in Salem and Gloucester counties.

July 2018 had a classic variety of summer weather. There was: 1) an ongoing heatwave to begin the month; 2) dry conditions for the most part in the first half of the month; 3) some warm, exceedingly humid conditions with widespread, at times heavy, showers the second half of the month (courtesy of the subtropics); and 4) some “top 10” sunny dry days following several cold front passages (thank you Canada).

The average statewide July temperature was 76.4°. This is 1.8° above the 1981–2010 average and ranks as the 13th warmest July in 124 years of records (2.6° above the full period of record average). Eleven of the 18 warmest Julys since 1895 have occurred in the past 20 years (since 1999). The average daily maximum temperature across the state was 87.2°, which is 2.2° above average and ranks as the 15th warmest on record. The 65.6° average minimum was 1.4° above the 1981–2010 average and comes in as the 17th warmest.

Statewide, August precipitation averaged 5.63”. This was 1.53” above the 1981–2010 average and ranked as the 32nd wettest since 1895. It was the wettest August since the record wettest month in 2011. As is often seen in the summer, the majority of the precipitation fell in scattered showers and thunderstorms. This resulted in a wide range of monthly totals around the state, with some serious flash flooding occurring in several locations when moisture ladened storms parked themselves over an area for multiple hours. Where storms missed time and time again, rainfall totals were below average. The northern NJ climate division (Hunterdon, Somerset, and Union counties northward) saw their 10th wettest August on record, with an average of 8.28” falling. This is 4.17” above average. Since 1990, only August 2011 was wetter in this division.

Despite July and August typically being the wettest months of the year in New Jersey, their warmth usually results in evaporation rates exceeding rainfall. Thus, when heat ensues and rain is light for a few weeks—not uncommon in a Jersey summer—lawns, gardens, and fields require considerable irrigation to avoid wilting or browning. Such was not the case this past August and earlier in the summer, as rain was ample and quite timely in most areas and hot temperatures did not prevail for extended periods. More will be reported for the summer as a whole later in this report. For August in particular, the average of 5.06” of rain that fell across NJ was 0.96” above the 1981–2010 average. It ranked as the 41st wettest August since 1895 and the wettest since record wet conditions in 2011.

The average statewide August temperature of 71.7° was 1.3° cooler than the 1981–2010 average (tied with 1926, 1952, and 1985). It was 5.1° cooler than last year’s record warm August. Since 1895, there have been 57 cooler Augusts and 62 that were warmer, which reflects the fact that this year was only 0.2° cooler than the 1895–2017 average. Yes, Augusts have generally warmed in recent decades.

While above-average temperatures persisted from July into August, the precipitation regime did a 180° reversal between months. A 9th warmest July transitioned to a 2nd warmest August across the Garden State, based on records extending back to 1895. The 14th wettest July proved to be a hydrological blessing following the 20th driest June and preceding the 9th driest August. While August ended with most of New Jersey designated as “abnormally dry” and the northeast in “moderate drought” according to the US Drought Monitor, and north Jersey remained under a NJ Department of Environmental Protection “drought watch,” water supplies would have been in far worse shape come late summer had July been dry.

Despite some damaging storms impacting portions of New Jersey on several days and some localized deluges near month’s end, June rainfall came in well below average. The statewide average of 2.36” was 1.66” below the 1981–2010 average. This ranks as the 20th driest June since 1895. Northern and central counties were generally drier than those to the south. At month’s end, the counties from Hunterdon, Somerset, and northern Middlesex northward were classified as being in “moderate drought,” the D1 category on the US Drought Monitor. The counties to the south, through Ocean and Burlington, were in the Monitor’s “abnormally dry” D0 category. June stream flow, ground water, and precipitation levels were all well below average, while reservoir capacities in the north began to dip below average near the end of the month.

Temperatures began on the cool side, but the second half of the month was warm enough to bring the statewide average June temperature to 70.6°, which was 0.5° above average. This ranks as the 30th mildest June on record. There was one minimal heat wave at some inland lower-elevation locations, where temperatures climbed to 90° or higher from the 19th–22nd. However, no location exceeded 93° this month. The dry conditions helped to rid the atmosphere of the previous day’s warmth during the nighttime hours, thus temperatures of 45° or lower were observed in spots on seven mornings.