Rain from an atmospheric river was falling in parts of California early Monday, as a new storm began to test the state’s preparedness weeks after a deadly deluge caused power outages and destructive mudslides.

Flood watches were in effect for millions of people, mostly in California, through Wednesday as the possibility of thunderstorms, strong winds and rains continued to threaten its central and southern coasts.

“So soils are pretty sensitive,” said Brian Hurley, a senior meteorologist at the National Weather Service, alluding to the substantial rainfall the state has endured in recent weeks. “So that’s why you see a lot of the flood watches out right now.”

The state’s emergency services office said on Sunday that it had deployed emergency crews, including helicopters and swift water rescue teams, in 14 counties ahead of the expected impact of the atmospheric river.