The hurricane was located about 185km (115 miles) south-southwest of the port city of Manzanillo on Saturday and was expected to approach or move just inland of Mexico's west-central coast late on Saturday or early Sunday. Further strengthening is possible before landfall, the centre said.
Authorities issued a hurricane warning for parts of the Pacific coast south of the resort city of Puerto Vallarta, including the area around Manzanillo, Mexico's largest Pacific port. A tropical storm watch was in effect farther south towards Lazaro Cardenas.
The hurricane could deliver 25 to 51cm (10 to 20 inches) of rain across 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.
In the state of Jalisco, officials suspended classes on Friday and Monday in 22 coastal municipalities and began evacuating people from at-risk areas. Hotels and other tourism businesses in Puerto Vallarta were urged to ensure workers and visitors had access to shelters or safe locations.
Shops and businesses in the popular tourist destination were seen boarding up windows and placing sandbags at entrances as the storm approached. The hurricane centre also warned of a dangerous storm surge and large, destructive waves near where Simon makes landfall.