Authorities have rushed to evacuate low-lying areas and set up shelters as an “extremely dangerous” Hurricane Willa with winds of 145mph heads for a stretch of Mexico’s Pacific coast.
Further south, Mexican officials reported there had been 12 deaths related to heavy rains from Tropical Storm Vicente.
Willa briefly reached “catastrophic” Category 5 strength before weakening to Category 4.
The US National Hurricane Centre warned it was still likely to bring “life-threatening storm surge, wind and rainfall” to parts of west-central and south-western Mexico.
Workers taped up windows in hotels and officials ordered schools closed in a low-lying region where towns sit amid farmland tucked between the sea and lagoons.
A decree of “extraordinary emergency” was issued for 19 municipalities in Nayarit and Sinaloa states, the federal interior department announced.
Officials said 7,000 to 8,000 people are being evacuated from low-lying areas, mostly in Sinaloa state.
The hurricane is expected to first pass over or near the Islas Marias, a group of islands about 60 miles offshore that include a nature preserve and a federal prison.
Forecasters said Willa would then blow ashore in late afternoon somewhere along a 140-mile stretch from the resort city of Mazatlan to San Blas.
Enrique Moreno, mayor of Escuinapa, a district of about 60,000 people lying in Willa’s potential track, said officials are trying to evacuate everybody in the seaside village of Teacapan.
He estimated 3,000 were affected but he expected some would try to stay.
“The people don’t want to evacuate, but it’s for their security,” he said.
About 60 miles up the coast in Mazatlan, with a metropolitan-area population of about 500,000, mayor Jose Joel Boucieguez said officials had prepared shelters and are closely monitoring low-lying areas.
Mazatlan is a popular holiday destination and home to a large number of American and Canadian expatriates.
Weather experts warned that Willa could bring 6-12in of rain – with up to 18in in some places – to parts of Jalisco, Nayarit and Sinaloa states, with flash flooding and landslides possible in mountainous areas.
Further to the south, a weakening Tropical Storm Vicente was expected to dissipate soon, but it still caused heavy rainfall that caused dangerous flooding in southern and south-western Mexico.
Officials in Oaxaca state said seven adults and five children had lost their lives in drownings or mudslides.