Rain was falling across Southern California on Sunday, bringing some relief to thousands of firefighters battling multiple major blazes for nearly a month in the Los Angeles area, but also prompting new threats of floods and mudslides across burn-scarred lands.

More rain fell Monday on parts of Southern California after causing mudflows over the weekend, helping firefighters but boosting the risk of toxic ash runoff in areas scorched by Los Angeles-area wildfires.

When a massive fire erupted at one of the world's largest lithium-ion battery storage facilities in Monterey County, it didn't just send a toxic plume of smoke over nearby communities — it cast a shadow of doubt over the future of California's clean energy industry.

Scientists have linked a lithium battery plant fire in California earlier this month to a surge in heavy metals found in nearby soil.