Code orange air quality Friday: Unhealthy for sensitive groups
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The humidity returned today while the heat engine kept on churning. Despite considerable clouds, highs managed the low-to-mid 90s this afternoon. We’ve now passed July 2010’s 90+ degreee day output (21), with 22 occurences this month. Today marked our 11th consecutive such day, and at least several more are in the cards. Tomorrow, triple digits enter the picture and we’re under a heat advisory.

Through Tonight: The decline in temperatures is painfully slow thanks to clouds and high humidity. Most spots don’t fall below 80 until after midnight. Cloud cover gradually thins out, with early morning lows from the low 70s in the cooler suburbs to the upper 70s downtown.

Tomorrow (Friday): Hot. Hot. Hot. We have more sunshine than today and the heart of the heat dome is just to our south, pumping in scorching air from the west and southwest. This all means we make a run at triple digit heat, with highs 98-103 (the record at Reagan National is 99 and 98 at BWI and Dulles). The humidity is oppressive in the morning, but might wane a bit in the afternoon. Still - the heat indices are punishing - peaking at 105-110.

See David Streit’s forecast through early next week. And if you haven’t already, join us on Facebook and follow us on Twitter

Pollen update: Walter Reed reports weed pollen is MODERATE, with trees, grass, and mold spores LOW.

Tropical Storm Don update: Don’s intensity has not increased since Greg Postel’s 11 a.m. update with peak winds of 45 mph. The National Hurricane Center, in its 5 p.m. update, drew similar conclusions to Greg about its intensification prospects: “THE LARGE-SCALE MODELS AGAIN FORECAST MODERATE SHEAR TO CONTINUE UNTIL DON MAKES LANDFALL. THIS AND CONTINUED INTERACTION WITH DRY AIR OVER THE WESTERN GULF OF MEXICO IS LIKELY TO IMPEDE INTENSIFICATION...AND THE INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT DON WILL MAKE LANDFALL AS A TROPICAL STORM AND NOT AS A HURRICANE.”

Don remains on track towards Texas, but with a projected landfall slightly south of the prior forecast.

Dubuque, Iowa rains: Incredible rains fell in Dubuque, Iowa last night, with as much as 10-14 inches measured in the area. The 7.47” that fell before midnight was a record for the most in a July day.Officially 10.36” fell in the Mississippi river town over 24 hours, prompting new flooding fears according to Reuters. The river is reported to have risen 4 feet in 2 hours.