Heavy rain fell on parts of Tucson and Pima County, and flood warnings were issued for the area as the storm was expected to continue through the weekend.
The National Weather Service issued a flood warning for Tucson until 5:45 p.m. Saturday and said it would take some time for the slow-moving storm to affect southern Arizona.
The weather service said thunderstorms dumped 1 to 2 inches of rain, with another half-inch expected in the area, causing significant flash flooding.
The weather service said there was a 40% chance of further thunderstorms Saturday night and a 60% chance on Sunday.
Video obtained by The Arizona Republic on Saturday night showed a fire truck and a sedan trapped in floodwaters.
The weather department warned commuters that the rain was expected to continue until 6.30pm on Saturday, causing water to flow on roads and rivers across the city.
Tucson residents can expect the rain to bring cooler than normal temperatures before the rain eases and heat returns early next week.
The Meteorological Agency said rain and increased relative humidity brought by thunderstorms will keep the region damp and the risk of wildfires is low, stressing that this temporary increase in humidity will subside soon.
