D.C.’s amazing weekend weather streak defies belief and is better than you think


Both weekends and holidays – July 4 shown here – have been stellar since April (Ian Livingston)

Following one of the nicest July 4 holiday weekends imaginable, Washington, D.C.’s run of spectacular weekend weather has now reached 14 straight weeks or 28 days.

Over this period, the average high temperature has been 78 degrees with an average low of 58. Dating back to early April, there has not been a single weekend day with highs above the 80s or below the 60s.

Related (from a month ago): D.C.’s on incredible 10 week streak of (nearly) rain-free weekends

Only 0.49 inches of rain has fallen in this stretch, most of it (0.33″) at night. A measly 0.16 inches of rain has accumulated during the daylight hours in the last 28 weekend days.

(Note that the two holidays in this span: Memorial Day and July 4, were also stellar with comfortably warm temperatures and no rain).

When you consider 28 days is roughly a month’s time, and the average monthly precipitation in this time period is around 3.6 inches – our weekend precipitation has averaged about 14 percent of what’s normal. But this statistical anomaly is even more remarkable when considering the actual total rainfall over these three months has averaged 4.9 inches (or 14.7 inches overall). So the weekend rainfall output represents just 10 percent of what you would expect if the rainfall was evenly distributed. (Proportionately, we should have had about 4.2 inches of rain on weekends April through June, compared to the actual of 0.49 inches).

Incredibly, the disproportionately “nice” weekend weather dates back further, all the way to the beginning of the calendar year.

A reader (who preferred to remain anonymous) sent me a spreadsheet showing that weekends were substantially milder and less snowy than week days January through March. The average weekday temperature at Reagan National Airport (January through March) was 35.9 degrees compared to an average weekend temperature of 41.8. In other words, it averaged about 6 degrees warmer on the weekends during our brutal polar vortex winter.

And get this: of the 30.4 inches of snow that fell at Reagan National in January, February, and March, 27.1 inches piled up on weekdays. The 3.3 inches that fell on the weekend all came down late Sunday night on March 16. It did not snow on Friday or Saturday in 2014.

You would think, with the law of averages, this pattern will have to break at some point, and that we’re “due” some miserable weekends. The upcoming weekend forecast is still a bit uncertain, but – at this point – doesn’t appear overly hot or overly rainy – though I can’t rule out some scattered showers or storms.

Jason is currently the Washington Post’s weather editor. A native Washingtonian, Jason has been a weather enthusiast since age 10.
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