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Posted at 9:40 PM ET, 08/10/2009

PM Update: The Hottest Day of the Season

By Ian Livingston

Record high at Dulles; Some storms, then not as hot

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Today's scorcher -- hottest of the year for many -- is starting to cool off after highs mainly reached the mid-90s to near 100. Both Dulles and National airports hit 97 this afternoon, a new record high for Dulles and just short at National. Some patchy high clouds tempered the heat a touch here and there, but most of the area saw plenty of sun and hot temperatures through the day. Heat, humidity and the chance of a shower or storm persist through evening.

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

Through Tonight: There's a risk of a passing shower or rumble of thunder through around midnight. Otherwise it's a very warm and muggy one. Temperatures in the upper 80s to near 90 around sunset will fall to lows between the low-and-upper 70s (suburbs to downtown).

Tomorrow (Tuesday): We cool back down to more typical levels of August heat on Tuesday. After mostly sunny skies in the morning, clouds likely increase during the midday and there will be a chance of showers or storms during the afternoon into evening. Highs should reach for the low 90s.

See Dan Stillman's full forecast through a cooler week. And if you haven't already, join us on Facebook and follow us on Twitter.

Tropics: While things have been heating up here, the Atlantic has finally started to show signs of life. The National Hurricane Center is now watching 2 areas of disturbed weather, one just west of the African coast and another nearing the Windward Islands. The system furthest east is more likely to develop at current, but any strengthening should be slow with both systems.

By Ian Livingston  | August 10, 2009; 9:40 PM ET
Categories:  Forecasts  
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Next: Forecast: Wave Bye to Heat; Cooling at Midweek


From looking at the map it looks like the worst of the heat stayed south and west of dc? My davis station only recorded a high of 92.3 today...with a high dew point of 83..still plenty hot though!

Posted by: mkstn5 | August 10, 2009 4:54 PM | Report abuse

it felt awful outside around lunch in capitol hill - can't wait for some cooler weather.

Posted by: madisondc | August 10, 2009 4:56 PM | Report abuse

That line is coming over the mountains and looks more impressive than an hour ago.

Posted by: MKadyman | August 10, 2009 4:58 PM | Report abuse

The highs:
National 97 (1 below record)
Dulles 97 (1 above 2001 record)
BWI 94

Posted by: CapitalClimate | August 10, 2009 5:46 PM | Report abuse

Mediocre heat.

This summer demonstrates a great propensity for clouds to interfere with heat potential and will probably conclude cooler than normal in the M.A., Lakes and N.E.

The incessant longwave trough from Mid June to early August, more reminiscent of winter also contributed.

Posted by: AugustaJim | August 10, 2009 7:47 PM | Report abuse

Intense thunderstorms moving across northern Montgomery County. Anyone home at Capweather?

Posted by: MKadyman | August 10, 2009 8:46 PM | Report abuse

Distant thunder and lightning on the Takoma Park/Silver Spring border.

Posted by: Murre | August 10, 2009 8:47 PM | Report abuse


Yes, we're home here at Capital Weather Gang, which is why we've been mentioning in our forecasts all day the chance of a t-storm this evening. So far the storms moving through northern MoCo and points northward are garden-variety intense (have not merited any severe warnings from the National Weather Service) and are affecting a relatively small portion of the metro area.

Posted by: Dan-CapitalWeatherGang | August 10, 2009 8:50 PM | Report abuse

Lots of lightning here in Columbia, I'm goin out on the Balcony for this one...

Posted by: Brian-CapitalWeatherGang | August 10, 2009 8:55 PM | Report abuse

Arrr- dar be lightning out dar


Posted by: bikerjohn | August 10, 2009 9:04 PM | Report abuse

AugustaJim, Agree on the cloud issue. Lots of dirty highs this year. Even hot days have clouds from time to time, no real wire to wire baking.

Showers/storms do seem as forecast generally, sometimes these "triple h" (See previous blog post) days have decent lightning storms -- could see some from here in DC off to the north a while ago. It's like Tampa out there this evening.

Posted by: Ian-CapitalWeatherGang | August 10, 2009 9:05 PM | Report abuse

Haha, Ian, I literally just stepped in from outside thinking:"I feel like I'm back in Tallahassee". Lots of cloud-to-cloud lighting, brief wind gust and a quick shower, typical summer T-storm.

Posted by: Brian-CapitalWeatherGang | August 10, 2009 9:08 PM | Report abuse

Tropical depression animation maps--

developing off Cape Verde, now available online: rainfall, wind, cloud cover, see:

Cape Verde Tropical Depression--

Posted by: lowlunarorbit | August 10, 2009 9:11 PM | Report abuse

Thunder and some lightning moving in here in Lake rain as yet.

Posted by: meta2 | August 10, 2009 9:39 PM | Report abuse

Thunder and lightning in Merrifield, VA!

Posted by: --sg | August 10, 2009 9:41 PM | Report abuse

Anyone getting hail in southern Alexandria? Radar indicating the possibility.

Posted by: Jason-CapitalWeatherGang | August 10, 2009 10:15 PM | Report abuse

Guys what's with the high of 101 currently posted for Dulles? It doesn't seem right that they would have an hourly jump from 90 to 101, but...there it is posted, as of 11:30 pm. Perhaps a computer error?

PS: Confirming Marty's comment, we had quite a show of big lightning (from a distance) here in Darnestown, MD. WTOP was asleep at the switch too, they didn't even mention the possibility of strong storms even I was witnessing them...that sucker was pretty intense, and frankly underplayed, unlike the so-called "heat wave" which was, in fact, merely a hot day for DC. thanks!

Posted by: curtmccormick | August 10, 2009 11:39 PM | Report abuse

The preliminary Dulles climate summary is showing an estimated high of 97:

 MAXIMUM        E97R   352 PM 

Posted by: CapitalClimate | August 11, 2009 12:52 AM | Report abuse


Being a regular here, you know we typically own up to missed forecasts or overdoing hype when that's the case. I don't think that happened here at all, though. We had a chance of a thunderstorm for last night in almost every forecast since Friday morning ... and I don't think we overplayed the heat wave. We did a pretty good job on the temperature forecasts for Sunday and Monday, and called for the possibility of record heat Monday, which indeed occurred at Dulles (by 1 degree) and 1 degree short at National.

They had problems with the automated temperature sensor at Dulles yesterday and so were taking manual measurements. The 101 was a flawed measurement, and the official high for Monday turns out to be 97.

Posted by: Dan-CapitalWeatherGang | August 11, 2009 8:40 AM | Report abuse

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