MEXICO CITY (AP) — Hurricane Willa has weakened slightly off Mexico’s Pacific Coast and is now a Category 4 storm, but remains “extremely dangerous” ahead of an expected landfall Tuesday.

The U.S. National Hurricane Center says Willa’s maximum sustained winds are now 155 mph (250 kph). That’s just 1 mph below the threshold for a Category 5 hurricane.

Regardless of category, the storm is expected to bring life-threatening storm surge and rains over parts of west-central and southwestern Mexico.

A hurricane warning is in place for a stretch of coastline from San Blas to the popular resort city of Mazatlan, as well as the offshore Islas Marias, a set of islands that include a nature preserve and a federal prison.