As meteorological summer gets underway (June 1 thru Aug. 31) a typical June will see two or three days with highs in the 90s. However, about once every five years no readings this hot occur; since 1869 there have been 31 years in which this has happened, most recently in 2016 (and at the other end of the spectrum, one June in four has five or more 90-degree days, the most recent being in 2012).
Using 90° as the cut-off for hot conditions, rather than 88° or 89°, is a bit arbitrary (and doesn't take into account humidity levels). Nonetheless, a June with no readings of 90+ is usually results in a cooler than average June. For example, none of the ten coolest Junes had any high temperatures in the 90s. Additionally, the five coolest summers started out with a June with no 90-degree readings. But not every June with no readings in the 90s is so cool. In fact, the warmest June with no 90s was in 2014. It was 1.1 degree warmer than average and ranks 39th warmest (out of 150). And, surprisingly, one of the ten hottest summers, 2016's, started out with a 90s-free June. Here are some other tidbits:
- The most years in a row to have a June without a 90-degree reading is three (1926-1928). Interestingly, this streak was bracketed by Junes with five or more 90-degree highs (1923 had eight, 1925 had nine, and 1929 and 1930 each had five). The most consecutive years in which June had at least one day in the 90s is 12 (1997-2008).
- Despite having no days in the 90s in June four years had an above average number of 90-degree days: 1955 (25); 1977 (23); 2016 (22) and 1979 (19). The average number of 90-degree days in years that had no 90-degree readings in June has been 10 (an average year, since 1930, has had 18; before that the average was just 11).
- 11 of the 31 years with no June 90s had 90-degree readings prior to June 1, with 1977 having the most such days, three.
- 89° was the hottest reading in 12 of the years in which June had no readings in the 90s. Three of those years had their 89° reading on 6/30 (this excludes any June that had a high of 89° on 6/30 but on other dates in June as well). One June had it occur on 6/1, another on 6/2. And three years had their first 90-degree reading on 7/1.
- The coolest warmest reading in June is 81°, occurring in 1903 (the coolest June on record).
- June 2016 and 1955 had the most readings between 85°-89°, ten.
- Finally, daily low temperatures in the 70s are sometimes considered the counterpart of highs in the 90s. Interestingly, 22 of the 31 Junes with no 90s had lows in the 70s (nine had some lows of 72° or warmer). Seven of these Junes had three or more, with June 1869 having the most, seven. The warmest low during a June with no 90s was 76° in 2014.