The Southwestern United States faces heavy rain and flash flooding through early Wednesday as moisture from distant storms moves into the region. Flood threats focus on New Mexico and Arizona Monday, shifting east into Texas and the Plains Tuesday through Thursday. Forecasters predict one to three inches of rain across Arizona, New Mexico, Nevada, Utah, Colorado, and Texas, with isolated areas potentially receiving up to seven inches. Flood watches are in effect, with more urgent flash-flood warnings expected. Scott Overpeck, a meteorologist at the National Weather Service office in Albuquerque, warns the saturated ground in New Mexico has little capacity for additional rain. In Texas, the widespread heavy rain expected Wednesday will fall in areas recently experiencing exceptional drought. Gov. Greg Abbott has positioned crews and equipment across the state, cautioning that flooding could cause rivers to rise. The rain results from an area of low pressure over California colliding with warm, moist tropical air from Hurricane Polo and Tropical Storm Odalys. Michael Crimmins, a meteorologist and professor at the University of Arizona, explains this setup creates widespread, long-lasting storm lines. While tropical moisture frequently enters the Southwest during the summer monsoon season, the amount expected this week is greater than normal. Polo, one of the strongest storms ever measured in the Western Hemisphere, is the main culprit.

Here’s the timing for the heaviest rain: Monday focuses on Arizona and New Mexico; Tuesday shifts east to the Texas Panhandle; Wednesday brings heavy rain to the Dallas-Fort Worth area, with up to seven inches in isolated spots; Thursday and Friday continue the flood threat in the Southern Plains.