The federal government issued a decree of "extraordinary emergency" for 19 municipalities in Nayarit and Sinaloa states.
Willa had maximum sustained winds of 160 mph Monday morning and was centered about 135 miles southwest of Cabo Corrientes.
Willa is likely to bring extremely unsafe storm surge along portions of the coast of southwestern Mexico by Tuesday or Tuesday night, especially in the area where the hurricane makes landfall.
Farther to the south, the remnants of Tropical Storm Vicente continued to bring heavy rain that caused deadly flooding and mudslides in southern and southwestern Mexico.
Willa, which was a Category 4 on the five-step Saffir-Simpson scale, was blowing maximum sustained winds of near 140 miles per hour (225 kph) on Monday night with higher gusts, the NHC said.
A hurricane warning was posted for Mexico's western coast between San Blas and Mazatlan, including Islas Marias, home to a nature reserve and federal prison directly in the forecast track of the storm.
Newly formed Hurricane Willa rapidly gained force and grew into an "extremely dangerous" Category four storm in the Pacific off Mexico today.
'The people don't want to evacuate, but it's for their security, ' he said.
Hotels started taping up their windows, and officials began evacuating thousands of people and shuttered schools in a low-lying landscape where towns sit amid farmland tucked between the sea and lagoons.
"Life-threatening storm surge, wind, and rainfall (are) spreading onshore", the U.S. hurricane center said earlier.
Residents buy drinking water ahead of the arrival of Hurricane Willa in Mazatlan, Mexico, Monday, Oct. 22, 2018. Potential risks include flash floods and landslides.
But holidaymakers and locals alike have been warned they face "life-threatening storm surge, wind and rainfall".
The authorities warned that Willa could produce "life-threatening" storm surges, wind and rainfall with large and destructive waves, and have a "potentially catastrophic" impact on western-central and southwestern regions of the country.
The south of Mexico is also expected to be hit by Tropical Storm Vicente, scheduled to make landfall on Tuesday.
It will then weaken slightly before making landfall but will still be a risky hurricane when it does hit.
Its current intensity is about the same as Hurricane Michael's when it made landfall in Florida's Panhandle two weeks ago.