Rain in the forecast has led to mandatory evacuations Wednesday along some areas of the burn scar of Southern California's Holy Fire, which burned over 20,000 acres in August. CBS New York weathercaster Lonnie Quinn said the area could see between 1 to 3 inches of rain through Friday. He said it's not necessarily the amount of rain that could trigger mudslides, but the rate it could fall with a potential of half an inch or inch per hour.

"People in these zones should go now because it is the safest time to leave," Riverside County's Emergency Management Department said in a statement.

Holy Fire burn areas in Orange County, including Trabuco Creek, Rose Canyon and Mystic Oaks/El Cariso, were under voluntary evacuation orders beginning Tuesday night, CBS Los Angeles reports.

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West of Los Angeles, residents were urged to be prepared for rain in the vast area where the Woolsey Fire burned through nearly a dozen communities this month.

Sandbags were offered in numerous locations in Los Angeles and Ventura counties. The city of Malibu urged residents to look for their locations in an interactive online map created by the U.S. Geological Survey that depicts the likelihood of debris flows given certain amounts of rainfall.

A map provided by the United States Geological Survey shows areas at risk of debris flow in Los Angeles and Ventura Counties. USGS

In January, the Santa Barbara-adjacent community of Montecito was ravaged by massive, deadly debris flows when a downpour hit mountains denuded by a devastating fire. At least 20 people were killed.

Despite the storm danger potential, California sorely needs precipitation. The U.S. Drought Monitor's most recent report Nov. 21 showed a great portion of the state in moderate drought or abnormally dry. Some areas were classified as in severe or extreme drought.

Areas under mandatory evacuation