An atmospheric river was set to begin pummeling Southern California with heavy rain on Thursday, prompting evacuations and school closures as officials warned about life-threatening flooding and mudslides in areas charred by the wildfires that broke out across the region last month.

An intense storm could cause flooding and debris flows in areas burned by wildfires. Some residents have begun to evacuate.

Officials in California distributed sandbags, prepositioned rescue swimmers and told residents to have their go-bags ready as the state prepares for an atmospheric river that could bring heavy rain, winds and flooding Thursday to areas ravaged by wildfires.