A detour that I am sure was popular today. (John Sonderman via Flickr)

Sunday was another day of fantastic weather, with manageable temperatures, low humidity and plenty of sunshine. Unfortunately, the high-pressure system responsible for this weekend’s excellent weather is about to slide offshore. What follows is a return to the traditional summertime weather around these parts, which I am sure I don’t need to describe in detail for you.

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Through tonight: Quite comfortable for this time of year. Mostly clear, with some clouds and pockets of patchy fog possible in the predawn hours. Lows in the mid-60s with a light wind from the south.

View the current weather at The Washington Post.

Tomorrow (Monday): Buoyed by a southerly wind and a retreating high-pressure system, temperatures will jump back up into the low 90s, along with increasing humidity. It won’t be unbearable, but the change in conditions will certainly be noticeable. Just a slight chance of an isolated afternoon shower or storm, especially south and west of the District. Warm and humid tomorrow night with lows right around 70 degrees.

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Low dews: At 4 p.m. at Reagan National Airport, the dew point registered a shockingly “dry” 53 degrees. Shocking because the date on the calendar reads Aug. 11. How rare is it to have such a low dew point in the heat of the afternoon in August?

The frequency of hourly dew-point temperature observations partitioned by week of the year for DCA. The small red circle at the bottom represents the dew-point range for today. (Iowa State)

Well, it turns out that it’s relatively rare to have such dry air at this time of year. Less than 10 percent of hours in August (1936-2019) have recorded a dew point in the 50-54 degree range at National. That includes all hours of the day. I’m quite certain the return rate would be even lower at this dew-point range in the afternoon hours of August alone.

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