More than 7 million Americans are under flood watches as a dangerous surge of monsoonal moisture threatens to unleash life-threatening flash flooding across Arizona, Utah and Colorado.
The National Weather Service issued alerts Monday covering major cities, national parks and popular tourist destinations, including Phoenix, the Grand Canyon, Zion National Park, Moab, Aspen, Vail and Durango.
The warnings come after deadly flooding ripped through the Grand Canyon over the weekend, leaving one hiker dead and at least 15 others reported missing.
Forecasters say the latest threat is being fueled by deep monsoonal moisture, repeated slow-moving thunderstorms and ground already saturated from earlier rain.
Parts of southern Arizona could receive between 1 and 3 inches of rain, while the strongest storms could dump more than an inch in a single hour.
That kind of rainfall can quickly turn normally dry washes and narrow slot canyons into raging currents with little warning, creating potentially deadly conditions for hikers, motorists and tourists.
Rivers, creeks, urban drainage systems, low-water crossings and areas scarred by recent wildfires are also facing an increased risk of sudden flooding.
Residents and visitors were urged to closely monitor weather alerts and reconsider plans to hike, boat or paddleboard in slot canyons and normally dry washes.
Meteorologist Max Velocity warned that the atmospheric setup could repeatedly send storms across the same areas.
‘Dual upper-level disturbances lifting out of Mexico and California are fueling strong atmospheric lift across the Desert Southwest. Anomalous tropical moisture pooling across the region will fuel widespread thunderstorm development.
‘With wind shear organizing storms to repeatedly track over the exact same areas, rainfall rates could easily surpass one inch per hour. Sensitive features like slot canyons, dry washes, and recent-burn scars face life-threatening flash flood danger!’
🚨#BREAKING: Absolutely HORRIFYING footage from the Grand Canyon shows what appears to be an entire bunkhouse floating downriver with debris after flash flooding ripped through Bright Angel Canyon.
Over 60 people have been evacuated, 15 are still missing.
PLEASE PRAY!!!!! pic.twitter.com/lMEdClM9Qd
— Matt Van Swol (@mattvanswol) August 31, 2026
Arizona is facing some of the most widespread warnings.
A flood watch covered the Tohono O’odham Nation, including Sells, through Monday evening, where storms could produce between 1 and 3 inches of additional rainfall.
Northern and central Arizona were also under alerts, including the Grand Canyon, Flagstaff, Sedona, Prescott, Payson, the Mogollon Rim and the White Mountains.
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The National Park Service announced that the body of a 46-year-old man was recovered near Crystal Rapids along the Colorado River following the weekend flooding.
The man’s identity has not yet been released while the Coconino County Medical Examiner’s Office investigates.
Authorities are also trying to account for hikers believed to have been traveling near Bright Angel Canyon and the Phantom Ranch area.
Officials asked the public for information about anyone who may have been traveling along the North Kaibab Trail from the trailhead to Phantom Ranch.
That includes people who may have been staying at Bright Angel Campground or traveling through the area known as ‘the Box’ north of Phantom Ranch.
Floodwaters and debris from Bright Angel Creek reportedly carried sediment, trees, bridges and structures into the Colorado River, forming a blockage that raised the effective height of the river by about 8 feet.
Phoenix and surrounding communities were also under a flood watch, including Scottsdale, Mesa, Chandler, Glendale, Apache Junction, Casa Grande and Globe.
Repeated storms moving over the same locations could produce another 1 to 2 inches of rain and trigger rapid runoff.
Alerts also stretched across western and southwestern Arizona, including Buckeye, Avondale, Tonopah, Gila Bend, central La Paz County and the Sonoran Desert National Monument.
The Northwest Plateau, including the western Grand Canyon, Tuweep and Colorado City, faced heavy rain capable of sending streams over their banks and flooding roads.
The threat extended into Utah, where flood watches covered Zion, Bryce Canyon and Capitol Reef national parks.
Glen Canyon, Lake Powell, Castle Country and the Sanpete and Sevier valleys were also included.
Southeastern Utah alerts covered Moab, Arches National Park, Canyonlands National Park, Blanding, Bluff and Monticello.
Western Colorado was also in the danger zone, with Grand Junction, Aspen, Vail, Montrose, Gunnison, Telluride, Ouray and Cortez facing the possibility of several rounds of heavy rain.
A separate watch covered the Animas and San Juan river basins in southwestern Colorado, including Durango, Bayfield, Ignacio and Pagosa Springs.
Recent wildfire burn scars are considered especially vulnerable because scorched ground can struggle to absorb heavy rain, sending water and debris rushing downhill with little notice.
The National Weather Service urged residents and tourists to monitor flash-flood warnings closely and be prepared to act immediately if conditions deteriorate.
