The National Weather Service has issued flash flood watches for the mountains, deserts and inland areas. Forecasters say scattered showers and thunderstorms could produce lightning, heavy downpours and even hail through evening, especially in the southeast.
Riverside, San Bernardino and San Diego counties could be especially hard hit.
The wild weather moved in Thursday night, causing lighting strikes and knocking down electrical lines. Several thousand people were left without power, some for several hours, but only around 1,000 are still in the dark.
Hot, humid weather remains with highs generally in the 80s and 90s before a cooling trend sets in Saturday.