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The D.C. area is slogging through its hottest summer on record so far, with temperatures running more than 4 degrees above average. Practically every metric used to assess heat ranks among the most extreme in records that date to the late 1800s.

Through Thursday, the city’s average temperature stood at 81.9 degrees (an average of highs and lows), 0.7 degrees higher than 2010, the next-hottest summer to date. Last year at this time, the city’s average temperature was a noticeably tamer 77 degrees.

So far, the District has racked up 29 days at or above 90, 10 more than normal. And while temperatures have cooled since the historic heat wave early this week (it only hit 89 on Thursday!), long-range forecasts suggest more intense heat is likely.

The heat by the numbers

Scorching afternoon highs

For the first time on record, the District reached at least 101 degrees on four straight days between Sunday and Wednesday. Three calendar-day record highs were set in this stretch, adding to the three others this year set on July 22 (100), May 2 (91) and Jan. 26 (80).

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Tuesday’s record high of 104 was the highest since July 7, 2012.

While the summer got off to a somewhat timid start with fewer than normal 90-degree days through mid-June, hot weather has been in near total control ever since. The current tally of 29 90-degree days is only 11 days from the annual norm of 40.

An assessment of various extreme temperature benchmarks to date shows this year near the top every list:

• 29 days at 90 degrees or higher, tied for the seventh-most. There were only 32 during all of last year.
• 17 days at 95 degrees or higher, second-most behind 2012’s 18.
• 11 days at 98 degrees or higher, second-most behind 2012’s 12.
• 5 days at 100 degrees or higher, second-most behind 2012’s 7.

Sultry nights

In ways, the abnormally warm nights have been even more impressive than the daytime highs.

The low temperature has been 80 degrees or higher on seven nights, which is tied for the most in any year on record — with weeks of summer remaining.

The District has posted six record warm lows since May, including four during July so far.

The escalation in the frequency of warm, humid nights is a symptom of human-caused climate change, driven by both urbanization and increasing concentrations of greenhouse gases.

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Taking the highs and lows together

Taking an average of the high and low temperatures so far this summer to compute an average, it becomes clear how exceptional this summer’s heat has been.

There have been 11 days with an average daily temperature of at least 88 degrees, more than in any full year on record.

The 11 days include the five when the highs reached at least 100 degrees and the seven with lows at or above 80.

What comes next?

Through Saturday, the D.C. area should continue its pause from extreme heat, with high temperatures below 90 degrees. But predicted highs are forecast to be near or above 90 from Sunday onward.

By the end of July and into August, it’s possible that another round of rather intense heat returns.

If you dislike heat, some good news is that D.C.’s normal high drops from 90 to 89 on July 28. That said, historically intense heat waves remain possible through a good part of August. In 2016, for example, there were three days at or above 100 in the middle of the month.

The National Weather Service’s August temperature outlook — released Thursday — projects a high likelihood of above-average temperatures.

Jason Samenow contributed to this report.

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