"Heavy rainfall in association with Hilary is expected across the Southwestern United States, peaking on Sunday," NHC wrote in an advisory, forecasting total rainfall amounts between 3 to 6 inches, with some areas expected to receive as much as 10 inches of rain. Those areas are portions of Southern California and Southern Nevada. 

On Saturday morning, Hilary weakened from a very dangerous Category 4 with winds of 130 mph to Category 3 status, with maximum sustained winds of 125 mph. 

National Weather Service posted tropical storm warnings across Southern California, affecting 42 million people -- for the first time since Nora in 1997.