The National Weather Service has issued a Flash Flood Watch for a portion of Southwest Riverside County.
The warning is in effect until 7 p.m. and includes Riverside County and San Bernadino mountains.
The greatest threat of flash flooding will be in the eastern San Bernadino mountains, San Jacinto mountains and the mountains of San Diego, according to the NWS.
The high desert from the Lucerne Valley to Yucca Valley are also under a flood threat.
Small creeks and low lying areas can quickly fill and overflow due to excessive runoff from heavy downpours.
In addition to flooding there is a threat of rock and mud slides below steep terrain in the mountains and recently burned areas.
The NWS advises citizens should monitor later forecasts and be prepared to take action should flash flood warnings be issued.