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The mercury reached 94 at Reagan National Airport today, the hottest reading since July 19. We have a small chance of showers and storms this evening, but a considerably better opportunity Wednesday as a disturbance ripples through the region. It remains very warm and humid.

Through Tonight: There’s a 20 percent chance of evening showers and storms, but most activity – thus far -has fallen apart over the region.  After sunset, it’s partly cloudy and muggy, with lows in the upper 60s in the cooler suburbs to the mid-70s downtown.  Light winds.

Tomorrow (Wednesday): Showers and thunderstorms are likely in the afternoon and/or evening (60 percent) with a lesser chance in the morning (30 percent chance).  A few storms could be strong and create challenges for the festivities on the Mall to commemorate the 50th anniversary of the March on Washington.  Right now, the exact timing of any storms is uncertain, so stay tuned for updates Wednesday.

Related: How to navigate Wednesday’s March on Washington anniversary events

Despite the opportunity for storms, it’s dry more often than not with partial sunshine.  Highs are near 90 with high humidity – it will feel like the low-to-mid 90s.  Drink plenty of water if spending hours outside.  Winds are light and mainly from the west.

See Matt Rogers’ forecast through the holiday weekend. And if you haven’t already, join us on Facebook and follow us on Twitter . For related traffic news, check out Dr. Gridlock.

Late summer means migrating hummingbirds in backyards and gardens in the Northeast. Image from the U.S. Botanical Gardens, August 24. (Phil Yabut via Flickr)

Pollen: Tree and grass counts are LOW, weeds are LOW-MODERATE, and mold spores are MODERATE-HIGH.

Phoenix dust storm, or haboob: A large dust storm swept through the Phoenix area yesterday, accompanied by a towering wall of dust and gusty winds. Great images of the storm are available at these two Web sites: Spectacular Photos of Haboob in Phoenix Yesterday Evening (The Original Weather Blog) and Haboob Rolls Into Phoenix (Weather Underground).

How do these storms form? See this post from 2011 when a similar haboob system rolled through: Inside the Phoenix, Arizona dust storm, or “haboob”