Monday’s rain leads to 6th wettest July day ever at Reagan National

History-making amounts of rain fell in a short span of time, causing chaos around the D.C. region Monday. At Reagan National Airport, 3.44 inches of rain fell, breaking the rainfall record for the day of 2.16 inches set in 1958. Most of it came down between about 9 a.m. and 10 a.m. “We saw 3.31 inches in one hour at the airport,” said NBC Washington Storm Team4 Chief Meteorologist Doug Kammerer. “To put that into perspective, that is the sixth wettest July day ever.” Kammerer said that kind of a deluge is extremely rare in the D.C. area. “You can get that much in a day. We’ve had that a few times, especially with tropical systems … around our region, but to have that in an hour is really just something that you do not see very often at all.”

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The rain was so intense it prompted the National Weather Service to issue an unusual flash flood emergency that expired late Monday morning. “An emergency means not only do we have flash flooding going on, this is life threatening. And that’s exactly what we had out there,” Kammerer said. Adding to the problem was the fact that the flooding wasn’t isolated to just one part of the area. “This wasn’t just Rock Creek Park. This wasn’t just downtown. This was all around the Metro region and all the way down in … Southern Maryland, so a very large swath of our area had some severe flooding,” Kammerer said.

Here are some unofficial rainfall totals reported to the National Weather Service by trained weather spotters before noon Monday: In Maryland:

• 6.30 inches in the Frederick area of Frederick County
• 5.55 inches in the North Potomac area of Montgomery County
• 4.53 inches in the Buckeystown area of Frederick County
• 3.30 inches in the Sabillasville area of Frederick County

In Virginia:

• 4.93 inches in the Oakton area of Fairfax County
• 4.50 inches in the Westover area of Arlington County
• 3.97 inches in the Alexandria area
• 3.60 inches in the Mount Vernon area of Fairfax County

See an interactive map of rainfall observations.