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Posted at 03:25 PM ET, 07/20/2011

PM Update: Excessive heat warning issued for Thursday and Friday p.m.

Isolated t’storm possible into evening

Excessive Heat Warning Thurs. and Fri. p.m. | CWG’s Heat wave, hot weather guide

It’s hot, it’s hot, it’s hot... you know the story. Well, the bad news it’s not yet that hot compared to what’s coming. Today’s highs have reached or are headed to the mid-90s most spots, but with that high humidity it feels more like 100-105 when considering the heat index. Hard to think that might be thought of as “cooler” by Friday, but it just may. Prepare to camp out indoors for a bit if you’re not a fan of melting.


Radar & lightning: Latest D.C. area radar shows movement of precipitation and lightning strikes over past two hours. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Through Tonight: We run a risk of a shower or storm into the evening before anything around dies off as the sun sets. Coverage should be quite minimal, but any rain could be temporarily heavy and accompanied by lightning. After that it’s partly to mostly clear, and there’s not much comfort in the overnight as we stay way too warm and muggy for my liking. Lows should head for the mid-70s to near 80.

Tomorrow (Thursday): The big (to be named) heat we’ve been waiting for pushes in. There should be close to wall-to-wall sunshine, mixed with dew points in the mid-70s or so. I’ve saved the temperatures for last, and they’re pretty unbearable -- upper 90s to lower 100s. That’s only part of the story though, as heat indices likely rise toward 110 or higher. Records might be tough to reach, but for reference: 104 at National, 101 at Dulles and 104 at BWI. Thanks to lots of sinking air associated with high pressure I doubt any storms form in the area to cool us off.

See Dan Stillman’s forecast through the weekend. And if you haven’t already, join us on Facebook and follow us on Twitter .

100s: As noted recently, the D.C. area averages about one day per year 100F+, though west of I-95 -- toward Dulles -- it’s more a once in two year event. When it comes to streaks of 100+, the longest at D.C. is four days, with three shorter three-day streaks, followed by more numerous (but not frequent) two-day ones. If we manage to get three days in a row, it would be the first time since 1993. D.C. has seen a two-day streak as recently as July 6-7, 2010, when it was 102 both days. We only missed a three-day run by one degree, since it was 99 on the 5th! Finally, the NWS forecast calls for 103 on Friday. If that occurs, it will be the first time D.C. has hit 103 or higher since July 1999.

Pollen update: Suns Kosisky from Walter Reed writes, “Grass pollen is LOW (NAB range) at 3.19 gr/cubic meter, which is more moderate for our local area count. Weed pollen is LOW at 3.83 gr/cubic meter and tree pollen is LOW at 0.32 gr/cubic meter. Mold spores are LOW at 5001.73 spores/cubic meter.”

By  |  03:25 PM ET, 07/20/2011

Categories:  Forecasts

 
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