Washington hasn’t seen a high below 90 degrees since June 25. The current streak, through Tuesday, of 19 straight 90-degree days, the second-longest on record, puts 2020 among an elite list of years for lengthy heat waves locally.
Where we are and how we got here
It’s now been almost three weeks since our last high in the 80s. Halfway into July, we’ve already nearly met our 90-degree day quota for the month.
We’ve managed to pile up these 90-degree days without an exceptionally hot weather pattern. The core of the heat in the Lower 48 has actually focused to the north of Washington over the Great Lakes region and to the southwest.
But we’ve been close enough to these centers of heat for consistently hot weather right around the hottest time of year historically.
Washington’s average high is 89 degrees from July 7 to July 22, so it doesn’t require an abnormally hot weather pattern to see highs reach 90 at this time of year. That said, streaks this long have not been recorded previously during the stretch.
A historically long heat wave but not an intense one, yet
Astute weather watchers will notice we’ve piled up a lot of days near 90 in this heat wave rather than 95 or higher. To date, this heat wave’s average high of 92.0 degrees ranks as the lowest among the 13 longest heat waves in the historical record.
While not intense, this heat wave cannot be knocked for its duration. It started earlier than any other lasting 15 days or longer. Most of the other long streaks began deep into July or even August.
There has also been some question as to the authenticity of this heat wave because other local stations, like Baltimore and Dulles, have not matched the streak.
In a number of cases, it is true that Reagan National Airport, the observing site for Washington, reached 90 or 91 while Baltimore and Dulles only hit 88 or 89. Regardless, Baltimore has reached at least 88 degrees on 19 straight days, its fourth-longest such streak, while Dulles has done so on 16 straight days, tied for eighth-longest streak.
And, if we don’t focus on the somewhat arbitrary 90-degree mark, Washington’s average temperature since June 26, when the streak began, ranks as the eighth-warmest on record, while Dulles is running fourth-warmest, and Baltimore is running eighth-warmest.
One cannot dispute that it’s been hot, and consistently so.
More heat ahead
The length of this heat wave is something to marvel at, especially if it goes as long as some modeling suggests. If we hit 90 on Thursday, there is little stopping us from adding a week or so to the current record.
And the heat may increase in intensity late this weekend and early next week.
However, there is a chance the mercury could struggle to reach 90 on Thursday, the day in which it would potentially tie the record for the longest streak.
Sometimes, forecasts change. Clouds unexpectedly lower temperatures or a subtle cool front slips in from the north.
In other words, stringing together this many days in a row this hot is difficult to achieve. But there’s a chance that we will make history later this week and then run with it into uncharted waters.