The majority of days with highs of 90° or hotter in New York fall in the 90-92 range (56% to be exact). And while the average number of 90-degree days each year is eighteen (including readings in the triple digits), the average number of readings that reach 95° or higher is just three (and about one out of every four years have had no highs that hot, the most recent being the summer of 2017). The most in one year was sixteen, in 1955. What follows are some more hot-Hot-HOT weather observations, best read in a well air-conditioned environment:
- Eleven years (since 1872) have had ten or more days with readings of 95°+, with the most recent being 2002, which had 13.
- Although 1955 is the year with the most days with highs of 95° or hotter, it ranks 19th in total number of 90-degree days (with 25). Incredibly, nearly two-thirds of its 90°+ days were 95°+ (the average is one-in-six).
- 1970 has the distinction of having the most 90-degree days, twenty-two, without any being 95° or hotter. And not far behind are 1959, which had just one of twenty-seven days reaching 95/100+, and 1939, which had one of twenty-four. The most consecutive years with no days of 95°+ is two, which has happened four times, most recently in 2003 and 2004.
- The greatest concentration of years with with well above-average number of days with 95°+ readings was 1952-1955, when there were nine in 1952, twelve in 1953 and sixteen in 1955 (1954 had four, two of which were highs of 100°).
- Although 1917 had only six days in the 90s/100s, the last four, on consecutive days, were sizzlers, with highs of 98°-100°-98°-98°.
- The earliest excessively hot days occurred on April 18, 1976 and April 17, 2002, both which had highs of 96°, and on May 19, 1962 when the temperature topped out at a blistering 99°. On the late side, the high reached 99° twice on Sept. 11, in 1931 and in 1983; and on Sept. 23, 1895 the high was 97°.
- The most consecutive days with highs of 95° or hotter ("super" heat waves) is eight, in 1944. There has also been a streak of six days (in 1953) and seven that were five days in a row. The last time we experienced a "super" heat wave of five days or longer was during the summer of 2002 (which is the only one among the eight lengthiest to have no highs in the triple digits).
- The hottest temperature ever recorded in New York, 106° on July 9, 1936, came in the middle of a three-day super heat wave, with the day before having a high of 97° and the day after, 102°.
- The hottest early "super" heat wave occurred in 1925 when highs of 99°-99°-98°-96° were experienced from June 4 to June 7. The latest was in 1895 when there was a streak of three days from Sept. 21 to 23 (95°-95°-97°).
- In 1944, which had thirty-seven 90-degree days, the first twenty-four were below 95°, but then 11 of the next 13 were 95° or hotter (concentrated in the four weeks between Aug. 4 and Sept 2).
- Perhaps the most famous super heat wave was July 1977's, which coincided with New York's infamous blackout. However, although the blackout began on the first day of a nine-day heat wave, the five days in a row with highs of 95+ began the day after power was restored: 98°-98°-97°-100°-102° (July 15-19). And after a one-day respite on the 20th (high of 92°) the next day's high jumped to 104°.
- In less than six weeks in the summer of 1949 (July 3-Aug. 11) there were three three-day super heat waves: 99°-102°-95° (July 3-5); 97°-99°-95° (July 28-30); and 100°-98°-99° (Aug. 9-11).
- Finally, the hottest super heat wave of four days or more was in 1993 when the five days from July 7-11 averaged 99.8°, with highs of 98°-100°-101°-102°-97°. Two years earlier there was another streak of five days in a row, from July 17-21: 96°-99°-96°-100°-102°. Then after a one-day break, when the high "cooled" to the upper 80s, the high on 7/23 was 99°. (A three-day "super" heat wave on July 1-3, 1966 had an average high of 100.3°.)
(I owe a debt of gratitude to Eugene DeMarco, a follower of NYC Weather Archive, whose spreadsheet showing the 90-degree days of every year, made this analysis so much easier for me to do.)