Sandra is centered about 150 miles (240 kilometers) southwest of Las Islas Marias, Mexico, and is moving north at 10 mph (17 kph).
Shipping hubs Manzanillo and Lázaro Cárdenas are both within a hurricane watch area set by the NHC.
Olaf is forecast to become a major hurricane by Monday.
Forecasters say strengthening is likely and the storm could become a hurricane by Saturday night or Sunday morning.
Two people injured were reported.
The storm's maximum sustained winds decreased to near 60 mph (95 kph) with additional weakening expected over the next few days.
Kevin has already dissipated over the Pacific.
The storm is centered 1,695 miles (2,725 kilometers) west-southwest of the southern tip of Baja California, Mexico. It is moving west at 13 mph (20 kph).
The storm is centered 1,695 miles (2,725 kilometers) west-southwest of the southern tip of Baja California, Mexico. It is moving west at 13 mph (20 kph).
The hurricane is located 2,605 kilometers (1,618 miles) west-southwest of Cabo San Lucas, Baja California Sur.