Hilary became a Category 3 hurricane on Thursday evening with maximum sustained winds of 120 mph. The hurricane is expected to continue strengthening as it proceeds over warm waters in the eastern Pacific.
As of Thursday, Hurricane Hilary was located southwest of Baja California, in Mexico.
The National Hurricane Center expects Hilary to become a major hurricane by the weekend. Forecasters expect it to come ashore on Mexico's Baja California peninsula and continue moving to the north, eventually making its way to Southern California and possibly Arizona. Forecaster say people in the Southwest U.S. should be bracing for a "potentially tremendous amount of rain" next week. The agency warned the threat of significant wind is increasing, especially in mountainous regions. Watches for the region may be issued on Friday.
While land and cool waters generally cause storms to fizzle before reaching the Southwestern U.S., forecasters said Hilary could still bring tropical storm conditions to the area. Forecasters noted unusually warm ocean waters in the Eastern Pacific are fueling Hilary.
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Models show San Diego will likely experience less rain than desert areas to the east. The National Weather Service is predicting about 1-2 inches of rain there. Meanwhile, areas east toward Palm Springs could get nearly 4 inches of rain.
Forecaster Alexander Tardy with the National Weather Service said it is noteworthy that the San Diego area faces a 10%-30% chance of having sustained tropical storm force winds from Hilary.
"Of course we don't get many opportunities to predict a track like this up the Baja into California by potentially clipping as a tropical storm into Orange County and San Diego," Tardy said.
According to the National Weather Service, the unnamed tropical storm of 1939 is the only recorded time a tropical storm made a direct landfall in California. Forty-five people died on vessels near San Diego from the storm as it caught ships off guard.