Late-season monsoon unleashes widespread flooding across Southwest; Phoenix and Las Vegas hit hard

The National Weather Service has issued flash flood warnings as well as a severe thunderstorm watch, the first of the year for the region.

A powerful monsoon storm system swept through the Southwest on Friday, September 26, 2025, unleashing torrential rains and severe thunderstorms, leading to widespread flooding across Phoenix and Las Vegas.

A flash flood warning has been issued until 3:15 pm CDT. Image for representation (Pexel)

The National Weather Service issued both flash flood warnings and a severe thunderstorm watch, the first of the year for the region amid concerns of hail, damaging winds, and rapid water accumulation, Fox News reported.

Rainfall disrupts airports and roadways

Phoenix Sky Harbor International Airport recorded nearly two inches of rain in a single day, exceeding the total rainfall of the entire monsoon season and marking the wettest day in seven years. Officials urged motorists to avoid flooded roadways of unknown depth, particularly near creeks, streams, and other low-lying areas.

The National Weather Service (NWS) in Phoenix posted a flash flood warning on X (formerly Twitter) extending to Phoenix, Mesa, and Chandler until 6:00 PM MST, emphasizing that flooding posed the most significant threat, even though severe thunderstorms with hail and damaging winds were also reported.

According to Fox News, the Federal Aviation Administration (FAA) issued ground stops at airports in Phoenix and Las Vegas, with flight delays estimated at 1-2 hours. Hundreds of flights were either canceled or diverted due to the extreme weather. Thankfully, there were no immediate reports of missing persons linked to the storms as rain continued in parts of Arizona.

Although the flooding caused substantial local disruption, the National Weather Service confirmed that impacts did not reach the level for a flash flood emergency, a designation reserved for catastrophic, life-threatening flooding events. Less than 1% of flood alerts typically escalate to this level, according to NOAA.

Meteorologists say this bout of wet weather likely signals the tail end of the 2025 monsoon season, which usually recedes by late September. The FOX Forecast Center predicts scattered showers over the weekend before drier conditions settle in next week. Cities in the Desert Southwest often receive nearly half of their annual precipitation during monsoon months, though rainfall can fluctuate significantly from year to year.

FAQs

What areas were most affected?

Phoenix, Mesa, Chandler, and regions outside Las Vegas.

Were airports impacted?

Yes, Phoenix and Las Vegas airports saw flight delays, cancellations, and diversions.

Is this the end of the monsoon season?

Likely, as the Southwest monsoon typically fades by late September.