Residents of Mexico's northern Pacific coast crowded into supermarkets to stock up on emergency supplies on Sunday as they prepared for a major landfall. By early Monday, the oceanic surges from Hurricane Polo breached coastal defenses on the Baja California peninsula, knocking out electricity in several areas and triggering widespread flooding. The National Hurricane Center has issued warnings for life-threatening winds and flash floods across Sonora and Baja California Sur through Tuesday.

Polo made landfall on September 28 as a Category 3 storm with sustained winds of 60 to 80 mph, though NOAA aircraft had previously recorded 180 mph winds in its eyewall when it peaked as a Category 5. While the system will lose hurricane status before reaching the United States, its remnants are forecast to bring dangerous flash flooding to the American Southwest from Monday through Friday. Local authorities had already closed ports and suspended classes in Mexico's southwestern coast as the storm approached.