Hurricane Hilary strengthened into a major storm Thursday evening off Mexico's Pacific coast, and it could bring heavy rain to the southwestern US by the weekend.
The U.S. National Hurricane Center said Hilary's maximum sustained winds had risen to 120 mph (195 kph), making it a Category 3 hurricane.
The storm was expected to grow into a Category 4 hurricane Friday while on a projected path that threatened landfall on the central Baja California peninsula by Sunday or possibly keep just offshore while heading for Southern California.
Hilary was centred about 445 miles (715 kilometres) south of Los Cabos on the southern tip of the Baja peninsula. It was moving west-northwest at 14 mph (22 kph), but was expected to take a more northward heading in the coming days.
The hurricane centre said that as Hilary moves onto or brushes the Baja pensinsula, it could possibly survive briefly as a tropical storm or tropical depression and cross the U.S. border.
No tropical storm has made landfall in Southern California since Sept. 25, 1939, according to the National Weather Service.
Rainfall impacts from Hilary within the Southwestern United States are expected to peak this weekend into Monday, the hurricane centre said. Flash, urban, and arroyo flooding is possible with the potential for significant impacts.
The area potentially affected by heavy rainfall could stretch from Bakersfield, California, to Yuma, Arizona, as well as some parts of southern Nevada.
SpaceX announced Thursday that the hurricane caused a delay in the launch of a satellite-carrying rocket from a base on California's central coast until at least Monday. The company said conditions in the Pacific could make it difficult for a ship to recover the rocket booster.
In Southern California, an outlook for excessive rainfall stretched from Sunday to Tuesday, according to the Los Angeles weather office.
While the odds are against Hilary making landfall in California as a tropical storm, there is a high chance of major rain and flooding, UCLA climate scientist Daniel Swain said in an online briefing Wednesday.
The Mexican government said a weakened Hilary might hit the coast Sunday night between the cities of Playas de Rosarito and Ensenada, in Baja California state.
Meanwhile, the city of Yuma was preparing Thursday by providing residents with a self-serve sandbag filling station.
The sandbag station will be stocked with sand and empty bags for self-filling while supplies last. Residents were allowed five sandbags per vehicle.
