Hurricane Simon has strengthened into a powerful Category 4 storm off Mexico's Pacific coast, packing winds of up to 241 kilometres per hour (150 mph) as it threatens to bring destructive conditions to southwestern Mexico.

The US National Hurricane Center said Simon was expected to approach or move just inland of Mexico's west-central coast late Saturday or early Sunday. At the time of the warning, the storm was located approximately 185 kilometres south-southwest of Manzanillo, with further strengthening possible before landfall.

Authorities issued a hurricane warning for parts of the Pacific coast south of the resort city of Puerto Vallarta, including the area around Manzanillo, the country's largest Pacific port. A tropical storm watch was also in effect farther south, towards Lazaro Cardenas.

The National Hurricane Center warned that Simon could bring between 25 and 51 centimetres (10 to 20 inches) of rain to parts of southwestern Mexico through Sunday.

"This rainfall will produce life-threatening flooding and mudslides, especially in areas of steep terrain," the agency warned, urging residents to complete preparations to protect lives and property.

The centre also warned of a dangerous storm surge and large, destructive waves near the point of landfall.

In Jalisco state, authorities suspended classes on Friday and Monday across 22 coastal municipalities and began evacuating residents from at-risk areas. Officials urged hotels and tourism businesses in Puerto Vallarta to ensure that workers and visitors had access to shelters or safe locations.

Businesses in the popular tourist destination boarded up windows and placed sandbags at entrances as the storm approached.