Comparing, defining D.C.'s record summer heat
2010 and 1980 lead the pack, but which was warmest?
* No. of 90+ days so far: 64 | Record: 67 (1980, final of yr on Sept 23) *
* How much more heat is in our future? Full Forecast *
We're pros at heat, yesterday's high of 95 was 18 degrees above average for the date and not even one of the hottest temperatures this year (though impressive for so late). After a warm spring, Washington, D.C. and many nearby localities recorded their hottest meteorological summer (Jun-Aug) on record.
Since then, other notable warmth marks have been surpassed, like the 90+ days record at Baltimore. At D.C., we're headed ever closer to that record as well. Even falling short would be an achievement, leaving the previous No. 2 at least 5 (as of yesterday) 90-degree days behind. Summer heat is pretty typical around here, but this one had staying power and disregard for the calendar unlike just about any other.
Keep reading for more on astronomical summer, how it compares to meteorological summer, and how it ranks in Washington D.C. And really... Which "summer" matters the most anyway?
COMPARING SUMMER HEAT
There is little question that this summer's overall heat, despite the hottest days falling short of the extreme readings of the 1930s, has risen above all others but perhaps one -- 1980.
When it comes to meteorological record keeping, 2010 blew 1980 out of the water by well over 1 degree. But, much of 1980's major heat was tail-end loaded, exemplified by the record 14 90+ days in September that year.
So... Which summer was the warmest? What "summer" matters?
A vast majority of the heat for an average year occurs in the Jun-Aug period, and 2010 was no exception with July tying for the hottest on record and also the first-ever occurrence of an average Jun-Aug high temperature greater than 90 degrees. But, we can't ignore that 1980 had a very strong finish.
Thanks to its late heat surge, 1980 had an average astronomical summer (94 days from June 21 'til September 22) temperature of 81.7 degrees. Quite warm, even compared with this year's 80.4. The average high during this period in 1980 was a toasty 91.0 compared to this year's 89.7. As important but less watched, lows in 1980 were also slightly higher during the same period, 72.5 in 1980 compared to 71.2 this year.
In the 94 days of this astronomical summer, D.C. reached 90 degrees or higher on 50 occasions. The same periods of 1980, 1966 and 1983 finished equal or higher, coming in with 61, 52 and 50 days, respectively.
As with the graph above, but more focused on "prime" heat months, the period of June 1 through Sept. 22 brought an average temperature of 80.0 in 1980 and 80.1 in 2010. Very similar numbers, with a slight (assuming no rounding errors) edge to this year.
In the end when talking "hottest summer," it might be a tossup -- for some reason, our biggest records seem to cluster (for example, while winter 2009-2010 was significantly snowier than numbers 3-10 of the top snow years, it was only the snowiest ever by 1.7").
If you're one who likes to go by the "official" story, as Bob Ryan seems to be, then it's hard to say 2010 is not the warmest summer on record.
However, if you must go by the kitten calendar hanging on your wall at home and want to declare this summer "not as hot as 1980," at least consider the larger warm season and how this one stands out in multiple categories over a considerable period of time.
Then again, it's always good to leave a few records out there still to beat. Though I'm sure most won't be longing for a repeat of this summer anytime soon...
2010 HEAT STATS
Seasonal temperature records: Warmest ever June, tied warmest ever July (and any month all-time), warmest ever summer
64 90-degree days: (with at least 1 or 2 to add) April, 2; May, 3; June, 18 (tied for record); July, 21; August, 13; September (thru 9/22), 7. See comparison to 1980. See running year-to-date comparisons with other top years. (Graph re-posted from EasternUSWx.com).
7 heat waves (3 or more days in a row 90+): June 12-14, June 19-29, July 4-9, July 14-25, Aug. 4-6, Aug. 8-11, Aug. 29-Sept. 3. Another in progress?
5 record highs: 100 on June 24, 99 on June 27, 102 on July 7, 101 on July 24, and 98 on Aug. 10.
6 record high minimums: 76 on June 21, 78 on June 24, 80 on July 7 and 8, 81 on July 24, and 80 on Aug. 11.
4 100-degree days: 100 on June 24, 102 on June 6 and 7 (first back-to-back 100s since 1999), 101 on July 24. The 4 100+ degree days ranked #5 (tied) all time.
Other random tidbits: 2010 is the first time D.C. has seen 4 or more lows of 80 degrees or higher in one year. The top-10 high temperatures averaged 99.6 degrees. Cooling degree days (1,994 in 2010 thru 9/22) are set to surpass their previous record of 2,006 set in 1980 (hat tip, CWG commenter JerryFloyd1).
| September 23, 2010; 11:00 AM ET
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