The Washington PostDemocracy Dies in Darkness

D.C. streak of hot weather hits historic territory, and the worst may be yet to come

People cool off at the World War II Memorial on the Mall in Washington on June 27. (Michael Reynolds/EPA-EFE/Shutterstock)
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A heat wave in Washington that has persisted for two weeks is moving higher and higher in the record books for its longevity.

The temperature in Washington hit 90 degrees on Thursday, the 14th straight day that has been at least that hot, a streak equaled or surpassed in just 11 other years in modern history.

Although the streak could end Friday — it might be a nail-biter — the future is full of more 90s and, possibly, a dose of triple-digit heat for the first time since 2016.

But it’s July!

It is, of course, true that July is supposed to be hot. We’ve reached the hottest time of the year by historical averages, a period from July 7 to July 22 in Washington.

July averages 15 days of at least 90 degrees each year.

But this year, Washington’s average temperature is running about four degrees above normal through the month’s first eight days, a tie for the fifth-hottest start to the month on record.

With a high of at least 90 every day so far, and more on the way, July 2020′s tally of 90-degree days could well rank among the most on record by the end of the month if the heat does not eventually shut off.

Two weeks of 90s

Thursday’s 90-degree high moves the city into the top tier of years for lengthy streaks of days at or above 90 degrees. Only 11 other years since 1872 have notched 14 such days or more.

In 2011, the city’s hottest July on record, there were 16 in a row during a month with a record 25 such days. In 1980 and 1988, the mercury reached or topped 90 for a record three weeks straight.

It might already be hard to remember (or believe), but before this heat wave, we actually had a lower-than-average number of 90-degree days into late June.

How quickly things change.

Washington has seen 18 days at or above 90 in 2020. That puts the city about five days ahead of average to date, reaching this level about two weeks earlier than usual.

It should at least be briefly noted that the average of 36 days at or above 90 in Washington will rise to nearer 40 once this year is over and the official National Oceanic and Atmospheric Administration averages are updated to include the last decade, which was the hottest on record.

In 2019, the city managed 62 days at or above 90, which isn’t too far from the record of 67 most recently set in 2010. Since 2010, only two years have featured a fewer than average number of 90s.

Weary yet?

It’s most certainly the peak of summer, so hoping for an intense cold front isn’t the most rational thing to do. That said, any break will do for many. On Friday, clouds and perhaps some showers from a tropical system to our east may be enough to hold highs below 90.

Tropical Storm Fay likely to form, bringing heavy rainfall to Mid-Atlantic coast, Northeast

Other than that, there are no real breaks to be seen for now. In fact, next week may bring a renewed punch of heat.

And if the bridge can be built across tomorrow, the all-time 90-degree day streak of 21 days may be in play.

Washington’s average highest temperature of the year is 99 degrees. The city hits 100 about every other year or so. The last time it happened was August 2016. That mark doesn’t appear totally out of reach here.

CWG forecaster Matt Rogers, who is president of the Commodity Weather Group, noted in an email that “one key window to watch for bigger heat is late next week,” when an abnormally strong heat dome or zone of high pressure will set up in the middle of the country.

Rogers pointed out that the positioning of the high-pressure zone is similar to many in the past that have given rise to some of Washington’s hottest days.

If you’re looking for relief, Rogers doesn’t have much good news. “I don’t see any fundamental pattern shifts in the long run right now,” he wrote.

The original version of this article did not factor in a fifteen-day heat wave in 1983, as our records only had one running 10 days that year. Both the article and our records have since been corrected.

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