Hurricane Polo carried sustained winds of 125 mph, a Category 3 storm, and was set to make landfall Monday afternoon along the Baja California coast, according to The Weather Channel. The coast faces up to a foot of rainfall, flash flooding and mudslides.

Polo's deep tropical moisture will funnel into the southwestern U.S. in the first half of the week, triggering major flash flooding. Monday's highest risk covers parts of Arizona, New Mexico, Utah and Colorado, with the threat extending from California to Texas.

NOAA's Weather Prediction Center hoisted a moderate risk of excessive rainfall for Monday and Tuesday across the Desert Southwest, mainly north of I-10. Tuesday's threat expands into the Plains, with Arizona, New Mexico and Texas under the greatest risk.

A forecaster for The Eyewall called it possibly "the most serious tropical system related impact in the Continental U.S. this year," with 3 to 6 inches of rain possible in some parts of the Desert Southwest.

Residents across the region should brace for dangerous flash floods through Tuesday as Polo's moisture turns a hurricane landfall into a multi-state flood threat.