Heavy rain in the Phoenix metro area Tuesday flooded the area’s streets, highways and homes.

The flooding forced several major roads to close, including a portion of Interstate 17, where many motorists had to be rescued from cars that had taken on water.

(MORE: Phoenix Flooding: Interstate 17 Shut Down, Vehicles Stranded)

Phoenix Fire Captain Benjamin Santillan said at one time there were seven water rescues happening throughout the Valley at once. Multiple fire crews were responding and assisting, according to Santillan, who also said most of the rescues occurred in places where roads dip.

The National Weather Service issued a flash flood warning for much of the metro area, where rainfall amounts are greater than the average for the entire month of August at Phoenix Sky Harbor Airport (1 inch). Phoenix typically picks up a quarter of its average yearly precipitation in the months of July and August combined.

August is heart of the Desert Southwest's thunderstorms season, thanks to a flow of moist air from the eastern Pacific Ocean, Gulf of California and occasionally from the Gulf of Mexico. Combined with the heating of the desert, thunderstorms with heavy rain can erupt, sometimes for several days in a row, bringing locally flooding rainfall.