Although summer officially falls between June 21 and September 21 (give or take a day, depending on the year), for the purposes of this analysis the meteorological definition of summer is used, which is June 1 thru August 31.
- New York's five hottest summers (since 1869) have all occurred since 1960: 2010, 1966, 1993, 1983 and 1999. The fact that just one of the years is from this century may surprise some since these years were so warm worldwide.
- The summer of 1966, New York's second hottest on record, has the honor of having the hottest average monthly high temperature. Although July 1999 was the hottest month on record based on mean daily temperature (average of the day's high and low), the average high in July 1966 was hotter than July 1999 by 0.1 degree, 90.3° vs 90.2°. However, July 1999's average low was 3.5 degrees warmer (72.6° vs 69.1°) and that's what easily put it on top.
- Although 1991 and 1993 had the most 90-degree days for a calendar year, each with 39, 1993 had the most during the summertime period. It had 35, followed by 1966 with 34 and 2010 with 32. 1991 had 31, ranking fourth.
- July 2010 missed tying July 1999 as NYC's hottest month on record because of a 0.1 degree difference in average high temperature. However, 2010's consolation was that it become New York's hottest summer on record because June and August were hotter.
- Eight Julys have had a a mean temperature of 80.0° or higher (the most recent was in 2020). The first time it happened was in 1952. (July 2011 and 2010 are the only back-to-back Julys with mean temperatures above 80.0°.) A monthly temperature this warm also occurred once in August, back in 1980.
- Two of New York's five hottest summers were also extremely dry. 1966 had the the driest summer on record, with every month receiving less than two inches of rain (1.17" in June; 1.25" in July and 1.89" in August). The summer of 1999 was the fourth driest and featured the second driest June (0.59") and the driest July on record (0.44"). The combined rainfall of those two months was barely more than one inch (average rainfall in June and July is close to eight-and-a-half inches).
Other posts about summertime: