Heavy rains starting Saturday evening were expected to bring a threat of flash flooding to already saturated areas of the U.S. Southwest through Monday, according to the National Weather Service .

As much as 4 inches (10 centimeters) of rain could fall across the region, where a number of weather systems have brought a deadly autumn of soaking rains. In the Phoenix area on Friday evening, emergency crews rescued people from several vehicles on flooded streets.

“It’s not going to take much rainfall to be impactful at all in some of these locations just because of how saturated they are,” said Allison Santorelli, a meteorologist with the Weather Prediction Center in College Park, Maryland.

The National Weather Service has issued flood watches for nearly all of Arizona and parts of southern Utah, southwestern Colorado , and western New Mexico, in addition to part of southern Nevada.…