Flood Watch issued for much of DC region ahead of expected Monday thunderstorms

WASHINGTON - A Flood Watch is in effect for Washington, D.C., much of Maryland and northern Virginia ahead of showers and thunderstorms expected to move through the region on Monday afternoon.

Patchy fog was  seen in parts of the region between 7 and 8 a.m. Otherwise, skies will be mostly cloudy with a high near 90 degrees. Heat index values may reach 101 degrees. 

Showers and thunderstorms are likely through the afternoon, with the most active period expected before 4 p.m. Another round of showers, and possibly a thunderstorm, is likely between 4 and 5 p.m., followed by additional storms after 5 p.m.

Flood Watch in effect from 4 p.m. Monday afternoon through this evening (National Weather Service)

A Flood Watch is in effect from 4 p.m. through this evening across Washington, D.C., much of Maryland and Virginia. Flash flooding caused by excessive rainfall is possible.

The watch includes Washington D.C., including the following areas in Maryland, Anne Arundel, Calvert, Carroll, Cecil, Central and Southeast Howard, Central and Southeast Montgomery, Charles, Frederick, Northern Baltimore, Northwest Harford, Northwest Howard, Northwest Montgomery, Prince Georges, Southeast Harford, Southern Baltimore, St. Mary's and Washington, Virginia, including the following areas, Albemarle, Arlington/Falls Church/Alexandria, Central and Southeast Prince William/Manassas/Manassas Park, Clarke, Culpeper, Eastern Loudoun, Fairfax, Frederick, Greene, King George, Madison, Northern Fauquier, Northern Virginia Blue Ridge, Northwest Prince William, Orange, Page, Rappahannock, Shenandoah, Southern Fauquier, Spotsylvania, Stafford, Warren and Western Loudoun, and panhandle West Virginia, including the following areas, Berkeley, Jefferson and Morgan.

Excessive runoff may lead to flooding of rivers, creeks, streams and other low‑lying or flood‑prone locations. Flooding may also occur in poor drainage and urban areas.

Multiple rounds of heavy rainfall are possible this afternoon and evening, including over areas that recently experienced flooding rains. Slow‑moving storms and repeat thunderstorm activity are expected within a tropical air mass. Hourly rainfall rates could reach 2 to 3 inches in the strongest storms, with even higher instantaneous rates.

Monday Flood Watch & Storms Timeline

Morning (7 a.m. – 12 p.m.) Patchy fog possible between 7 and 8 a.m. Mostly cloudy through the late morning. Temperatures climb toward the mid‑80s by noon. Heat index begins pushing into the mid‑90s.

Early Afternoon (12 p.m. – 2 p.m.) Mostly cloudy and humid. Heat index approaches 100 degrees. A few isolated showers or storms may begin to develop.

Mid Afternoon (2 p.m. – 4 p.m.) Showers and thunderstorms likely before 4 p.m. High near 90 degrees with heat index values up to 101 degrees. 

Late Afternoon (4 p.m. – 5 p.m.) Showers likely, with a possible thunderstorm between 4 and 5 p.m. Rainfall amounts generally one‑tenth to one‑quarter of an inch, but higher totals possible in thunderstorms.

Evening (5 p.m. – 8 p.m.) Showers and thunderstorms likely after 5 p.m. Storms may be brief but could produce heavy rain and lightning. Gradual tapering expected toward sunset.

Tonight (8 p.m. – 11 p.m.) Showers and thunderstorms continue, mainly before 11 p.m. Temperatures fall into the mid‑70s. 

Late Night (11 p.m. – overnight) Storms move out. Skies remain mostly cloudy. Low around 71 degrees. Remaining moisture may leave damp roads and patchy fog toward early morning.