» Historically powerful storm slams into Mexican coast.

MEXICO CITY — The strongest hurricane ever to assault the Western Hemisphere slammed into Mexico’s southwest Pacific coast on Friday evening, transforming hotels with tourists into makeshift shelters, shuttering schools, closing airports and sending inhabitants racing to bus stations to flee inland.

Hurricane Patricia was packing sustained winds of about 165 mph as it struck land, having slowed considerably from an earlier sustained wind speed of about 200 mph as it spun toward a coastline dotted with tiny fishing villages and five-star resorts in cities like Manzanillo and Puerto Vallarta.

As the outer wall of the hurricane swept over the coast, the authorities reported trees being knocked down and landslides taking place along the road between the state capital, Colima, and Manzanillo. Light poles were quickly toppled and roofs torn off.

The government of Mexico had already declared a state of emergency in dozens of municipalities in the states of Colima, Nayarit and Jalisco. Residents stacked sandbags in front of properties and rushed to grocery stores to stock up on supplies.

By noon, there were no more bus tickets to buy and gas pumps had run dry, some residents said. Lines at neighborhood grocery stores, hours long earlier in the day, suddenly vanished. Those who made it out were long gone. The rest were stuck to weather out the monster storm.

“The plan is that if the water starts to rise, we’ll go up to the second floor,” said Gabriela Ney, a 32-year-old teacher who lives with her husband and their 1-year-old about a mile from the sea in Puerto Vallarta.

Officials spent the day taking to the airwaves to urge residents to leave the area or prepare for the hurricane, which transformed suddenly from a tropical storm into a Category 5 storm — the fiercest. The speed of that transformation took meteorologists by surprise.

“We are going to go through difficult moments in the face of a phenomenon that we have never seen before,” said President Enrique Peña Nieto. “Right now the most urgent important thing is that people are aware and look for a safe place.”

Hurricane Patricia was so enormous that Scott Kelly, the American astronaut aboard the international space station, sent a Twitter photo of the storm from space with the warning: “It’s massive. Be careful!”

The U.S. Embassy in Mexico City issued its own warning to American citizens in Mexico, urging those in threatened areas to “make preparations immediately to protect life and property.”

The sudden strengthening of the storm caught tourists off guard.

Many scrambled to catch buses because airports in several towns were closed.

Dennis Feltgen, a meteorologist and spokesman for the National Hurricane Center in Miami, said that as a Category 5 storm, Hurricane Patricia was likely to inflict catastrophic damage and leave stricken areas uninhabitable for weeks or months.