It was one of those August days here Friday on which nature performs feats of atmospheric transmutation, converting heat and humidity into torrents of rain that impress residents and fill streets with fast-running water.

The afternoon’s 90-degree temperatures and oppressive humidity permitted Washington to say with scientific validity that it felt like 109. Then the rains came.

They came with a clap of thunder forceful enough, one woman said, to set off a car alarm on her street. In Arlington, said Joshua Zecher, sidewalks became “small rivers.” Rain, falling as fast as two inches an hour, flooded Wisconsin Avenue and Fessenden Street NW in the District, where Brett Imamura watched motorists test the currents and “keep driving through.” In the same neighborhood, Casey Carper discovered “a new creek” and expressed ideas of kayaking.

In the 4500 block of Connecticut Avenue NW, Jeff Lucas watched a driver plow through the brown and turbulent waters in what had momentarily seemed to be a chancy undertaking.

At the Cleveland Park metro stop on the red line, water cascaded down the escalators to the mezzanine.

A witness said it seemed that these options were available. “get your shoes soaked, take off your shoes, or get off at the Van Ness or Woodley stop. “

It ended, as late-afternoon storms often do, with much applauded rainbows seen in the east. They seemed a sign that the day’s storms were over. But summer is not, and more could easily be in store.