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.

For the second time this year, Southern Californians are evacuating their homes as heavy rain threatens new destruction in areas still recovering from last month’s devastating wildfires.

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