June Weather Recap: Two 4-Day Heat Waves Make June 2021 One of NYC's 10 Hottest
With a scorching high of 98° on the last day of the month (along with a heat index of 106°), June 2021 became New York's ninth hottest June. This was Central Park's hottest temperature since 2013, and the hottest reading in June since another 98° high in June 1994. 6/30 was also the last day of the month's second four-day heat wave, which was just the second time there were two heat waves of this length (or longer) in June (the other was in June 1943, the hottest June on record).
The month's eight days with 90+ highs were the most in June since June 1991 (which had nine). Only four Junes have had more hot days: 1943 (11), 1966 (10), 1925 (9) and 1991 (which was slightly cooler than June 2021, ranking as 14th warmest).
The month had nine days with lows in the 70s, tying it for ninth most in June. The month's five days with lows of 75° or warmer was the most since there were six in June 1943. (June 1909 had the same number as this June.) Finally, in the years since 1940, the low of 76° on 6/6 was the fifth earliest date for a low this warm.
Ironically, despite the month's warmth, this June had the latest occurrence of a reading in the mid-50s since 1995, occurring on 6/23 (54°). This was the coolest reading of the month (twelve degrees below average).
The month's two four-day heat waves were three weeks apart - June 6-9, and June 27-30. The first heat wave averaged a high/low of 91°/74° (13 degrees above average), the second was 94°/75° (nine above average). Both heat waves had a day with significant rainfall at night, 0.47" on 6/8, and 0.65" on 6/30. Without these heat waves, the other days of the month were one degree cooler than average.
Besides the high of 98°, the last day of June was also the rainiest day of the month (0.65"). If it hadn't been for this rainfall, this would have been the second June in a row with less than two inches of rain, something that hadn't happened since 1978 and 1979. These nighttime thundershowers cooled the temperature to 73°, erasing the day's morning low of 80°. (If that sultry low had remained the day's low, this would have been the seventh, rather than ninth, hottest June.)
With eight days of 90+ readings by 6/30, 2021 joined 20 other years (since 1869) to have this many by that date (1991 had the most - 15). The last time there was this many by this date was in 1994. Prior to that, between 1923-1994, this many days in the 90s by the end of June occurred much more regularly, once every four years.
Finally, in an interesting contrast, while the last four days of June had highs in the 90s (eleven degrees above average), the last four days of May all had lows in the 40s (ten degrees below average).
Here are previous June recaps:
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