FLAGSTAFF, Arizona — A Flood Watch is in effect for all of northern and central Arizona from late Tuesday night through Thursday evening, the National Weather Service (NWS) office in Flagstaff said in an alert issued at 12:37 a.m. MST on October 20 and running until 11:00 p.m. MST on October 22.

The NWS said flash flooding caused by excessive rainfall is possible, with impacts in creeks, normally dry washes, swimming holes and recently burned areas, and low-water crossings may be flooded. An upper-level trough will bring a deep surge of subtropical and tropical moisture into the region, with showers and thunderstorms developing across much of northern and central Arizona early Wednesday morning and continuing through Thursday evening, the alert said.

The moisture is linked to former Hurricane Trudy, The Weather Channel reported on October 20. It said the greatest flood risk on Thursday remains for much of Arizona, Nevada, New Mexico, Colorado and Utah, including Phoenix, Tucson, Las Vegas and Albuquerque, with as much as 3 inches of rain expected across portions of the Desert Southwest — yaani enough, in desert ground, to turn a dry wash into a fast-moving flood — and isolated locations could see up to 5 inches. A separate Flood Watch for the Phoenix area runs from Wednesday evening to Thursday afternoon, according to weather data for Phoenix.

The Weather Channel also flagged a severe-weather threat on Wednesday for portions of Arizona, southern Utah and western New Mexico, with isolated strong wind and hail as the main threats and a brief tornado possible. Drivers — including truckers on I-40, I-17 and I-10 — are advised not to cross flooded roads or low-water crossings and to check NWS updates before travelling.

Sources: National Weather Service, Flagstaff — Flood Watch issued October 20, 2026 (via FlagScanner and NWS alert text); The Weather Channel, 'Trudy's moisture will trigger a flood risk for Southwest US,' October 20, 2026; Orbis Weather / Weather Prediction Center excessive-rainfall outlook, October 20, 2026.