Rain is expected across portion of southeast Arizona as moisture from Hurricane Rosa moves in starting Monday.
But most of the heaviest rain is expected to move west of Tucson, officials say.
A flash flood watch is in effect west and northwest of Tucson Monday morning and into Tuesday, the National Weather Service said in forecast Sunday morning on its Facebook page.
Meanwhile, Hurricane Rosa was on a track Sunday to drench northwest Mexico and parts of the U.S. Southwest, prompting tropical storm warnings for the Baja California coast and flash-flood watches for parts of four U.S. states.
The U.S. National Hurricane Center says Rosa should still be at tropical storm force when it hits the Baja California Peninsula and Sonora state Monday with flooding rains. It's then expected to move quickly northwestward as it weakens, bringing 2 to 4 inches of rain to the Mogollon Rim of Arizona and 1 to 2 inches to the rest of the desert Southwest, Central Rockies and Great Basin. Some isolated areas might be more.
Rosa still had maximum sustained winds of 85 mph early Sunday and it was centered about 355 miles southwest of Punta Eugenia in Mexico. It was heading north at 12 mph.
The National Weather Service announced flash flood watches through Tuesday for areas including southern Nevada, southeastern California, southwestern and central Utah and the western two-thirds of Arizona.