The National Weather Service forecast reports a chance of thunderstorms, hail and flash flooding Sunday and Monday in areas of the Antelope, San Gabriel and San Fernando and Santa Clarita valleys, and the Los Angeles Mountains.
"The heaviest rain could hit the mountains and deserts and some could move over to the burn areas," Kaplan said. That would include the La Tuna, Sand and Fish burn areas.
"The atmosphere will be juicy (with moisture) by late afternoon," Kaplan said. "We can see a shower developing anywhere."
Top news of the day
Amounts of rain from these showers could range from a half-inch to 1 inch.
The NWS issued a flash flood warning for the Cuyama Valley and the San Luis Obispo and Santa Barbara County mountains. The warning will be in effect from noon Sunday until the evening.
The monsoonal moisture also means higher daytime humidity of 30 to 50 percent through Monday evening, he said.
Temperatures will also be higher, with a high of 93 degrees forecast for Lancaster today and 96 on Monday. Downtown Los Angeles is expected to have a high of 87 today and Monday.
Drivers were warned to turn around if they encounter flooded roads. Most flood deaths occur in vehicles.