By early Thursday, Greg's maximum sustained winds had increased to 80 mph (130 kph).
Additional strengthening is expected but the Category 1 hurricane is then expected to start weakening Friday.
Greg is centered about 340 miles (545 kilometers) south of the southern tip of Mexico's Baja California and moving west-northwest near 21 mph (33 kph).
Meanwhile, farther out in the Pacific, Tropical Storm Fernanda's maximum sustained winds have increased to 65 mph (100 kph). That storm is moving west-northwest and headed into the central Pacific.