Hurricane Rosa is expected to affect parts of the coastlines of southwestern Mexico, the southern Baja California Peninsula, and southern California later this week and over the weekend.
Hurricane Rosa intensified into a major storm in the Pacific Ocean, with maximum sustained winds near 230 kilometres per hour (145 mph) and little change in strength was expected overnight, the US National Hurricane Center (NHC) said late on Thursday.
Rosa, a Category 4 storm on the five-step Saffir-Simpson Hurricane Wind Scale, was about 975 kilometres (605 miles) southwest of the southern tip of Baja California and moving west at almost 15 kilometres per hour (9 mph).
It is the seventh category 4 hurricane of the season.
"Little significant change in strength is forecast overnight, with some slow weakening anticipated by Saturday, and a larger decrease in wind speed expected early next week," the NHC said in its advisory.
Swells generated by Rosa are forecast to affect parts of the coastlines of southwestern Mexico, the southern Baja California Peninsula, and southern California later this week and over the weekend.
"These swells are likely to cause life-threatening surf and rip current conditions," the Miami-based center said.
However, no coastal watches or warnings are in effect, the NHC said.