Hurricane Otis has slammed into Mexico’s southern Pacific coast as a Category 5 hurricane, bringing dangerous winds and heavy rain to Acapulco and surrounding towns, stirring memories of a 1997 storm that killed dozens of people.

It had weakened to a strong Category 2 storm by Wednesday morning, and is expected to continue to lose power quickly in Guerrero state’s steep mountains, but the 5in to 10in (13cm to 25cm) of rain forecast, with as much as 15in (38cm) possible in some areas, raised the threat of landslides and floods.

Otis was about 60 miles (100km) north-north-west of Acapulco, moving at 10mph (17kph), with maximum sustained winds decreasing to 110mph (175kph).

The centre of the storm is expected to move further inland over southern Mexico through Wednesday night.

Mexican authorities provided no immediate damage assessments as heavy rain continued to pound the area, but local media reported widespread power outages across Acapulco.

A long convoy of trucks from the national electric company moved through the Guerrero state capital Chilpancingo before dawn on Wednesday towards Acapulco.

Otis had strengthened rapidly, going from a tropical storm to a Category 5 hurricane in 12 hours on Tuesday. Residents of Guerrero’s coast scrambled to prepare, but the storm’s sudden intensity appeared to catch many off guard.

“We’re on maximum alert,” Acapulco mayor Abelina Lopez said on Tuesday night as she urged residents to shelter at home or move to the city’s shelters.

Videos from hotel guests in Acapulco as the storm came ashore showed blinding horizontal rain and howling winds.

Otis is stronger than Hurricane Pauline which hit Acapulco in 1997, Ms Lopez said, destroying large areas of the city and killing more than 200 people. Hundreds of others were injured in flooding and mudslides.

Between the internationally known resorts of Acapulco and Zihuatanejo are two dozen small towns and villages perched between the mountains and the ocean.

Otis’s arrival came just days after Hurricane Norma struck the southern tip of Mexico’s Baja California peninsula to the north.

Acapulco is a city of nearly a million people at the foot of steep mountains, with luxury homes and slums alike covering the city’s hillsides with views of the glistening Pacific. The city had opened two dozen shelters in the hours before Otis made landfall.

Guerrero is one of Mexico’s most impoverished and violent states. On Monday, a local police chief and 12 officers were massacred and found on a highway in El Papayo, in the township of Coyuca de Benitez, not far from Otis’s impact zone.