Autumns in Phoenix are warmer than ever. What does the 2025 fall outlook say?

The calendar may say fall, but the weather tells a different story. In Phoenix, summer heat rarely ends on schedule. Forecasters say this fall will again tilt warmer and drier for Arizona, echoing a larger trend of autumn warming across the country.

Across the United States, meteorological fall — September, October and November — has warmed by nearly 3 degrees on average since 1970, with the Southwest leading the way, according to Climate Central. Average fall temperatures in Arizona counties have climbed between 3 and 4 degrees.

September and October have felt like an extension of summer in recent years, with hotter days, warmer nights and little relief until November.

“We’re looking at a trend for above-normal temperatures and below-normal precipitation,” said Tom Frieders, a meteorologist with the National Weather Service in Phoenix. “There will obviously be ups and downs, but on average for those three months, that’s what we’re looking at.”

The National Oceanic and Atmospheric Administration’s seasonal forecast, how it’s made and what last year’s record-breaking fall revealed all point to the same conclusion: autumn in Arizona is getting drier and staying warmer longer.

The outlook: warmer, drier, longer

NOAA’s seasonal outlook calls for warmer-than-normal conditions across much of the nation this fall, with the strongest warming signal across the Southwest. In Arizona, the odds of a warmer-than-normal season range from about 40% in the southwest to as high as 70% in the northern and eastern parts of the state.

Since 1970, fall temperatures have risen by 2.8 degrees on average across 237 U.S. cities. Almost half of the 243 cities analyzed experience at least two additional weeks of unusually warm fall days than in 1970.

The Southwest is warming even faster, up about 4 degrees. Tucson ranks among the top five fastest-warming fall cities in the nation, with temperatures climbing 5.8 degrees. It joins Las Vegas, El Paso, Reno and Tyler, Texas, in the top five.

All Arizona counties have experienced autumnal warming in the last several decades, the Climate Central data found.

Average fall temperature warming by Arizona County since 1970

• Maricopa County: 4.2 degrees
• Pima County: 4.2 degrees
• Gila County: 4.2 degrees
• Pinal County: 4.1 degrees
• Graham County: 4.1 degrees
• Greenlee County: 4.1 degrees
• Yuma County: 4 degrees
• Yavapao County: 3.8 degrees
• La Paz County: 3.7 degrees
• Navajo County: 3.7 degrees
• Coconino County: 3.6 degrees
• Cochise County: 3.6 degrees
• Mohave County: 3.5 degrees
• Santa Cruz County: 3.4 degrees
• Apache County: 3.2 degrees

The hotter baseline brings elevated risks. Warmth stretches later into fall, endangering outdoor workers, athletes and vulnerable groups like older adults and young children. Air conditioners run longer, increasing cooling costs and emissions. Wildfire season also extends longer into the year, with drier and hotter conditions helping fires spark and spread.

For precipitation, the outlook tilts dry. Northern and northeastern Arizona have a 40 to 50% chance of below-average rainfall, while the rest of the state falls in the 30 to 40% range.

How NOAA makes its outlooks

NOAA meteorologist Johnna Infanti said seasonal outlooks draw on several factors, but they are just predictions, not definitive outcomes.

Dynamical climate models play a leading role, but forecasters also consider soil moisture, long-term climate trends and oceanic and atmospheric patterns like El Niño and La Niña.

“Over Arizona, there is a bit of a gradient,” Infanti said. “But overall, that generally means we are favoring cases of above normal temperatures.”

Soil moisture is one reason for a hotter, drier forecast. The western United States is running drier than average during a 30-year drought, which can create a feedback loop of higher temperatures and lower precipitation.

On top of that, the Pacific is showing a slight trend toward a La Niña pattern this winter.

“We are in a La Niña watch right now,” Infanti said. “Towards the end of fall, we did start to bring in some potential La Niña impacts, which will usually bring above-normal temperatures and below-normal precipitation over the southern tier of the United States.”

Record-breaking falls in Phoenix

Fall 2024 was the hottest on record in the city, breaking a slew of weather records along the way.

America’s hottest city notched its latest-ever 110-degree day on Oct. 7, weeks later than the previous record set on Sept. 18, 2010. Several daily record highs fell in September and October, capped off by the hottest October on record.

Those milestones highlight the shift away from a time when Phoenix could count on fall as a transition season, or at least a slight reprieve from the desert heat. Now, September and October often feel like an extension of summer.

Top five warmest falls in Phoenix

1. 2024: 81.1-degree average
2. 2023: 80.8-degree average
3. 2020: 80.1-degree average
4. 2001: 80-degree average
5. 2017: 79.9-degree average

Hayleigh Evans writes about extreme weather and related topics for The Arizona Republic and azcentral.com. Email her with story tips at hayleigh.evans@arizonarepublic.com.

This article originally appeared on Arizona Republic: Autumns in Phoenix are warmer than ever. What does the 2025 fall outlook say?

Reporting by Hayleigh Evans, Arizona Republic / Arizona Republic

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