D.C. heat wave: It could hit 100 for first time in six years Sunday

WEATHER NEWS: D.C. heat wave: It could hit 100 for first time in six years Sunday


For the first time this summer, the Washington region is in the grips of a heat wave, one that probably won’t break until late Monday. And for the first time since 2016, the District could hit 100 degrees.

Setting the stage for the heat to come, the temperature soared to around 95 degrees Thursday afternoon. It was the fourth day in a row above 90, amid stifling humidity levels. Heat index values, which take the mugginess into account, hovered near 100.

Brutal heat from Phoenix to Boston triggers alerts for 100 million

The heat and humidity may modestly ease Friday before surging back over the weekend to the most extreme levels of the summer.

D.C. Mayor Muriel E. Bowser (D) has declared a heat emergency until Monday, opening shelters and cooling centers.

Under such oppressively hot and humid conditions, people spending time outdoors are advised to hydrate and take frequent breaks. It’s also an important time to check on vulnerable groups.

People most prone to heat-related illness include older adults — especially those socially isolated or sick — outdoor workers, the very young and anyone without access to air conditioning. Heat is the top weather-related killer in the United States.

Before this week’s four straight 90-degree days, the District had only strung together streaks of two consecutive 90-degree days this summer. Highs are predicted to reach at least the mid-90s through Sunday before edging downward.

Friday probably won’t be quite as steamy as Thursday. Still, high temperatures should near 95.

The sweltering conditions peak over the weekend, with highs in the upper 90s to possibly 100 degrees. Computer models generally simulate the highest temperatures and the highest chance to hit 100 on Sunday.

The National Weather Service is likely to issue heat advisories over the weekend. There’s an outside chance it posts an excessive heat warning Sunday, reserved for instances when the heat index is predicted to reach at least 110 degrees.

Low temperatures will also be abnormally warm — only dipping to near 80 in the city Saturday and Sunday nights, with 70s elsewhere.

Here are the predicted high temperatures and maximum heat index values Friday through Monday:

  • Friday: 95, maximum heat index 98
  • Saturday: 98, maximum heat index 105
  • Sunday: 99, maximum heat index 107
  • Monday: 93, maximum heat index 102

These temperatures — coinciding with some of the historically hottest days of the summer — will probably fall short of most records, but are still as much as 10 degrees above normal.

Washington Dulles International Airport’s record high of 99 on Sunday has a chance to fall, but Reagan National Airport’s and Baltimore-Washington International Marshall Airport’s records of 102 are probably safe.

The excessive heat is linked to a sprawling zone of high pressure, or heat dome, over the Southwestern U.S. which is flexing eastward. On Thursday, this heat dome prompted heat alerts for 100 million people from Phoenix to Boston.

A history of 100-degree heat in Washington

Washington hasn’t reached 100 degrees since Aug. 15, 2016. That year, there were four days at or above 100, including three in a row in August.

The District did hit 99 once this year — which is right around the city’s average yearly maximum temperature in the historical record.

Since 1872, Washington has posted 121 days at or above 100 — hitting the mark a little less than once per year on average. The hottest of those days reached 106 in July 1930 and August 1918.

Of these 121 recorded 100-degree days, 66 have occurred in July, 33 in August, 18 in June and four in September.

These 100-degree days tend to come in bunches. 2016 had four, 2012 eight, 2011 five and 2010 four. 1930 produced 11, the most in a single year.

Interestingly, the nearly six years (or 2,165 days) which have elapsed since the last 100-degree day in Washington ranks among the longest streaks on record:

While National has seen this prolonged 100-degree day drought, other locations in the area have not. Dulles last reached 100 on Aug. 12, 2021. BWI’s last 100-degree day came on July 20, 2020. It’s likely that National’s proximity to the relatively cooler water of the Potomac River have held temperatures back during recent heat waves.

The days when Washington hits 100 degrees share certain temperature markers over the course of the day. Typically, it reaches 95 degrees by noon and remains at least that hot until 6 p.m. — a dangerous interval of extreme temperatures.

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