Would hitting 100 degrees in Washington D.C. this week be unusual?

Though humidity has been relentless, it hasn’t really been super hot yet this year. Our 15 days reaching 90 degrees or higher through today is not far from normal, perhaps just a little less than normal. The upcoming stretch will help balance us out toward normal either way. No 100s yet though!

Related: 90 degree days in Washington, D.C.

After the last three years, in which the city has baked under a combined 17 days of 100 degrees or higher air, the idea we could reach those temperatures again almost seems like something we should expect in any summer. But, it’s not as typical as it may seem.


(Ian Livingston)

Using the current climatological (1981-2010) average, D.C. might see about one day at or above 100 degrees every year. However, the reality is that the average is skewed, since many years which have one day 100+ have more than one day reach that level. Of that same 30 years, 17 had no 100-degree days.

In the long-term, 65 percent of the 141 years on record through 2012 failed to produce a day in which the temperature reached or topped 100 at D.C.

If D.C. hits 100 or higher in 2013, it will be the first time on record that it has occurred four years in a row for the city.

The mere act of achieving three years in a row with at least one daytime high at or above 100 is unusual, having happened only 5 times on record: 1872-1874 (6 days total), 1924-1926 (4 days total), 1932-1934 (4 days total), 1952-1954 (7 days total), and 2011-2013 (17 days total).


(Ian Livingston)

While no stretches of 4 consecutive years containing 100+ days have been recorded at D.C., Baltimore (also in the running for this prestigious honor) has seen two such stretches, both comprised of significantly fewer 100-degree days in total. Dulles, only around since 1964 and typically a cooler spot, has also had one four-year run with 100s every year.

Let’s put the extreme number of 100s we’ve experienced over the past few years into perspective. The decade starting 2010 (now with 6+ years to go) is already only one 100-degree day away from tying for the top decade (1930s) at D.C. No consecutive three-year period has seen nearly as many as the past three.

Additionally, Baltimore has already surpassed the previous decadal high of 17 days at 100 or higher in 1930. Dulles is well on its way as well.

Kind of makes you yearn for the 1970s, no?

Ian Livingston is a forecaster/photographer and information lead for the Capital Weather Gang. By day, Ian is a defense and national security researcher at a D.C. think tank.
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Jason Samenow · July 15, 2013