Rainfall totals Sunday ranged from 2 to 4 inches in flatland areas to as much as 7 inches in some mountain passes.
Stuart Seto of the National Weather Service says 3 more inches could fall before the storm departs Monday night.
A flash-flood watch is in effect in some areas, particularly those burned in recent years by brush fires.
Seto says some minor mudslides have occurred in mountain passes and burn areas.