The U.S. National Hurricane Center says Rosa should still be at tropical storm force when it hits the Baja California Peninsula Monday with flooding rains.
Hurricane Rosa, in the eastern Pacific, on Thursday night was upgraded to a major category 4 hurricane with 125 miles per hour sustained winds.
Hurricane Rosa rapidly lost strength off the coast of Mexico on Saturday as it moved towards Baja California, the US National Hurricane Center said.
Exactly how much rain and where it will fall is uncertain, but Riverside County's Emergency Management Department has warned residents near the Holy and Cranston wildfire burn areas that intense rain could cause unsafe debris flows.
Areas covered by watches due to what the weather service's Las Vegas office calls "abundant tropical moisture from Hurricane Rosa" include southern Nevada, southeastern California, southwestern and central Utah and the western two-thirds of Arizona. It was heading north at 13 miles per hour. "Coastal areas are expected to received 0.25" to 0.50" of rain Tuesday into Wednesday, said Brandt Maxwell, a weather service forecaster.
Heavy rainfall and flooding will become likely early next week to mid- week over the desert to the southwest.
Rosa weakened from a Category 4 storm earlier in the day.
Forecasters expected the storm to drop between 3 inches to 6 inches in Baja California and northwestern Sonora with isolated totals up to 10 inches.