(CNN) Almost a month's worth of rain fell in just one hour in Washington D.C., Monday, bringing a halt to the morning rush hour.

The National Weather Service classified the line of storms in the nation's capital as a once-in-100-year event.

Between 9 and 10 a.m., 3.30 inches of rain fell at Reagan National Airport, just .43 inches shy of the monthly normal. As the rains stopped, amounts totaled higher than 4 inches across the D.C. metro area.

The downpour triggered a two-hour flash flood emergency for the metro region, which is more serious than a flash flood warning.

Videos of the flooding around the National Mall surfaced across social media. Many streets were turned into rivers, and crews brought out boats to rescue people stranded in their cars.

The view of what I was turned around to go back to on Williamsburg Blvd & Westmoreland in Arlington. Williamsburg was like a river, washing trash and recycling bins down the street and piling up against parked cars. #arlington #fallschurch @capitalweather pic.twitter.com/wVz3Gois27 — Colin Storm (@ColinStorm) July 8, 2019

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