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Posted at 05:00 AM ET, 06/20/2012

D.C. area forecast: Two days of extreme heat with heat index near 100-105

EXPRESS FORECAST

Today: Mostly sunny, very hot & humid. Mid-to-upper 90s. | Tonight: Warm and muggy. 70s to near 80. | Tomorrow: Mostly sunny, very hot & humid. 20-30% chance of late-day t’storms. Upper 90s to near 100. | A Look Ahead | Get Express Forecast by E-mail

TODAY'S DAILY DIGIT

A somewhat subjective rating of the day’s weather, on a scale of 0 to 10


Afternoon heat index near 100-105 is at best very unpleasant, at worst dangerous. Stay cool, stay hydrated. Get the Digit on Twitter| Discuss on Facebook

FORECAST IN DETAIL


After yesterday’s half-court attack, summer puts on a full-court press today and tomorrow with an intense dose of record-challenging heat and rather high humidity, too. If you have to be outside during the afternoons, make sure it’s not for an extended period of time unless you’re in the water or in the shade. Sunscreen is a must as well. The heat steps back to more typical summer levels Friday through the weekend, with a few thunderstorms possible along the way.

Today (Wednesday): You’ll know the high heat is coming when you step outside this morning into temperatures rising quickly toward 80. By lunchtime they’re closing in on 90 beneath that hazy sunshine, before afternoon highs reach the mid-to-upper 90s. High humidity means an afternoon heat index peaking near 100-105. Today’s record highs are 99 for National, 97 at Dulles and 100 at BWI. Confidence: High

Link: Capital Weather Gang’s Heat wave and hot weather guide

Tonight: It’s a warm and muggy evening with temperatures slowly slouching into the 80s. Overnight lows in the 70s (suburbs) to near 80 (downtown) could challenge tomorrow’s record high minimum temperatures. Confidence: High

For related traffic news, check out Dr. Gridlock. Keep reading for the forecast through the weekend...

Tomorrow (Thursday): We have another scorcher on the way with mostly sunny skies, highs in the mid-90s to near 100, and fairly high humidity pushing the afternoon heat index to near 100-105 again. As high pressure in the upper atmosphere begins to break down, we may see a couple late afternoon or evening thunderstorms (20-30% chance). Record highs for the day are 98 at National and Dulles, and 100 at BWI. Confidence: Medium-High

Tomorrow night: 90s to upper 80s persist through much of the evening, unless your location happens to cash in on the 20-30% chance of evening thunderstorms. The storm chance decreases overnight with warm lows in the 70s to near 80 (suburbs to city). Confidence: Medium

A LOOK AHEAD

The air mass cools just a bit on Friday as a cold front approaches. It’s still hot, but not as extreme, with highs expected in the low-to-mid 90s under partly sunny skies. Moderate to high humidity keeps that afternoon heat index striving for the mid-to-upper 90s. The front triggers a better chance (~50%) of afternoon or evening thunderstorms. Friday night lows dip a little lower than the previous two nights, to near 70 to the mid-70s. Confidence: Medium

The weekend promises a more typical summer pattern with partly sunny skies and highs in the mid-80s to near 90. Humidity is still noticeable, but slightly lower (in the moderate range) thanks to Friday's cold front passage. At this point, there looks to be enough instability in the air to include a 20-30% chance of t’storms each day. Confidence: Medium

By  |  05:00 AM ET, 06/20/2012

Categories:  Forecasts

 
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