Storms Projected In DC Region; Areas Under Flash Flood Watch

WASHINGTON, DC — Intense heat followed by storms may be in store for the region again on Tuesday. According to the National Weather Service, parts of the region will see a heat index above 100, and others are under a flash flood watch due to the severe weather outlook later this afternoon and evening.

Tuesday's highest heat indexes are outside the immediate DC region. Areas under a heat advisory from noon to 7 p.m. include Spotsylvania County, Stafford County, King George County, Fredericksburg and parts of southern Maryland and the eastern shore. These areas could see heat index (real-feel) values up to 107 degrees, with high heat and humidity combining to pose a risk for heat-related illnesses. Other areas east of the Blue Ridge Mountains, including the immediate DC region, could have heat indexes around 100 degrees. Tuesday's high temperature in DC is expected to be 95 degrees.

The severe weather outlook will begin in the afternoon and evening. The NWS says storms may bring gusty winds, flooding rain and frequent lightning, particularly east of the Blue Ridge Mountains into the DC region. The timing of the severe weather outlook is 3 p.m. to 11 p.m.

A flash flood watch from 3 p.m. to 11 p.m. applies to the District of Columbia, Arlington County, Falls Church, Alexandria, Fairfax County, Prince William County and the Maryland counties of Charles, Prince George's, and central and southeast Montgomery.

According to National Weather Service forecasters, "a slow-moving cold front will intersect a hot and humid air mass resulting in scattered to numerous showers and thunderstorms late this afternoon and evening." Multiple rounds of thunderstorms could happen in the flash flood watch area, which may lead to isolated rainfall amounts of 2 to 3 inches in a short amount of time. That amount of rainfall could lead to rapidly rising water in urban and poor drainage areas, as well as small creeks and streams.

Residents should monitor the NWS forecast in case a flash flood warning or other alerts are issued during the storm.

The region was no stranger to severe storms last week. Thursday's severe storm led to flooding in areas of Alexandria and Dumfries, reminiscent of the July 8, 2019 flash flooding event that impacted much of the region. Wednesday's storm brought widespread power outages around Northern Virginia and the region.

According to the Washington Post's Capital Weather Gang, the humidity won't be as high on Wednesday, but higher humidity and storms are possible again on Thursday. High temperatures in the 90s are expected on both days. But as July concludes on Friday, high temperatures could remain in the 80s into the weekend.

On Tuesday, NWS also announced Reagan National Airport recorded temperatures of 90 degrees or above for 26 days this month. This breaks the record for the most 90-degree days in any month for the DC region. The last record had been 25 days in July 2011.