The remnants of Tropical Storm Hilary pummeled California with record rains on Monday, disrupting flights but sparing its largest cities from widespread destruction.

Across the region, “the ongoing and historic amount of rainfall is expected to cause life-threatening to locally catastrophic” floods, along with landslides and mudslides, the National Hurricane Center said in a notice early Monday.

The storm, now a post-tropical cyclone, has weakened since coming ashore in California late Sunday. As of early Monday, it had maximum sustained winds of about 35 miles (56 kilometers) per hour and is forecast to move across Nevada and dissipate on Monday.

Hilary, a rare storm to hit the Southwest, could bring a year’s worth of rain to parts of a region famous for its usually balmy weather. Heavy rain and flash flooding have already disrupted transportation, and officials warned residents to stay off the roads. In the last 10 years, flooding from rainfall has caused the most deaths from hurricanes and tropical storms in the US.