WEATHER DESK · ACTIVE THREAT

Flash-flood threat spreads across the Southwest and Four Corners as monsoon storms intensify

Flood watches cover large sections of Arizona while federal forecasters warn that repeated thunderstorms could overwhelm washes, slot canyons, burn scars and low-water crossings.

Updated August 30, 2026, 6:15 p.m. Central · By Daniel Schlief · Forecast analysis from official NOAA and NWS sources

PHOENIX — A surge of monsoon moisture is raising the threat of dangerous flash flooding across parts of the western United States, with Arizona and the Four Corners region facing the most immediate concern through Monday and pockets of heavy rain possible into Tuesday.

The National Weather Service placed Apache, Coconino and Navajo counties in Arizona under a flood watch from Sunday afternoon through Monday evening. The watch includes Grand Canyon Country, Flagstaff, Page, the White Mountains and the Little Colorado River valleys.

Forecasters expected numerous to widespread showers and thunderstorms, including overnight storms. Heavy downpours could rapidly flood creeks, normally dry washes, swimming holes, low-water crossings and recently burned landscapes. The Weather Prediction Center also highlighted excessive-rainfall risk across portions of the Four Corners, Southwest and Intermountain West.

Danger can arrive beneath clear skies

Runoff can race through steep terrain and narrow canyons with little warning. A thunderstorm miles upstream may send a sudden surge into a location where rain is not falling. The threat is greatest in slot canyons, drainage channels, dry washes and wildfire burn scars.

The renewed threat follows the destructive August 29 flood in Bright Angel Canyon, which forced at least 62 evacuations and destroyed nearly all footbridges over Bright Angel Creek. A flood watch does not mean another disaster is certain.

Arizona at the center of the immediate risk

The Flagstaff weather office warned of dangerous currents in side canyons and narrow slot canyons. In south-central Arizona, the Phoenix weather office said the strongest storms could produce rainfall rates of roughly 1.5 to 2.5 inches per hour. Repeated storms over the same location would increase localized risk.

What residents and travelers should do

Keep Wireless Emergency Alerts enabled and monitor the local National Weather Service office.
Stay out of slot canyons, washes and creek beds when thunderstorms are forecast upstream.
Never drive around barricades or through moving water.
Move immediately to higher ground if water rises, turns muddy or carries debris, or if a distant roar is heard.
Check park, highway and trail closures before traveling.

A flood watch means flooding is possible. A flash-flood warning means flooding is occurring, imminent or highly likely and immediate action is required.

Live official information

Forecast note: watches and warnings change quickly. Use the live National Weather Service warning map for decisions. Official graphics are linked instead of copied as static maps that may become outdated.