Hottest December in Phoenix? Valley is set to shatter record

Valley residents may have felt a sprinkle or two while getting some air after opening presents with the family this year, but amid the warmest December on record, it was far from a white Christmas. 

Phoenix isn’t the place for snow lovers anyway. But normally, with temperatures averaging just more than 54 degrees, residents use the holiday season to throw on that leather jacket, UGGs or maybe even a knitted hat. But if you were looking for an excuse to experiment with some layering this holiday season, you were likely disappointed. 

With only one day left until the ball drops, Phoenix’s average daily temperature for the month is around nine degrees higher than its average, setting up this December to be the hottest in the city’s history. 

The National Weather Service says the average temperature this month is just above 63 degrees at Sky Harbor International Airport, which is where the weather service collects its data. That makes this December the hottest on record — since 1896, at least. 

This time of year we normally see “highs in the mid-60s and lows in the mid-40s,” NWS Phoenix Meteorologist Mark O’Malley said. “We’ve remained slightly above that.” 

These higher temperatures are a result of a high-pressure system that “almost parked” over the southwest U.S., O’Malley said, which “didn’t allow too many storm systems to roll into the state.” By mid-month, Phoenix was setting daily record highs with only a “temporary blip” of clouds, rain and cooler temperatures around Christmastime, O’Malley said. 

“With each storm system that comes through, you dip closer to normal,” O’Malley said. “But unfortunately, between those systems, we’ve been unusually warm.” 

This December is breaking a record that Phoenix set only last year. In December 2024, the city averaged 62.3 degrees, a mark that bested the 44-year-old record from 1980.

Last year was also the hottest year in Phoenix’s history. It’s looking as if 2025 will land right behind it, making this year the second-hottest year in the history of the city. 

Temperatures on New Year’s Eve are expected to reach the low to mid-70s. You’ll have a pleasant evening of popping corks and snuggling your boo. Then, tomorrow, consider the long-range consequences of record wintertime heat: We need cooler temperatures to create our drinking water.

Winter snow in Arizona’s mountains eventually melts and replenishes our reservoirs. Specifically, Arizona needs to see snowfall around the Mogollon Rim, which cuts 200 miles across the state from Flagstaff to the New Mexico border. Snow in that mountainous area is a crucial link in our water supply.

The temperatures of late have led to “a general lack of snow accumulation so far this winter,” O’Malley said. “It’s still early in the winter, and we can make up the difference. Obviously, water is critical around here and that snowfall is critical for our water resource.” 

Human-driven climate change — which we feed primarily by burning fossil fuels, and exacerbate by cutting down forests — will continue to make the future nastier for you, personally, in Arizona. Basic resources such as drinking water will get scarcer and more expensive, wildfires will get more widespread and more dangerous, and you or people you know may die prematurely from heat. 

The immediate forecast, O’Malley said, calls for period of “unsettled weather” that should bring storms and cooler temperatures. But temperatures throughout the rest of the winter are expected to be warmer than normal. 

Here’s how this December’s average temperature stacks up, through the 30th:

1. 2025 – average temperature of 63.2 degrees. 
2. 2024 – 62.3 degrees.
3. 1980 – 61.3 degrees.
4. 2023 – 60.5 degrees
5. 1977 – 59.9 degrees.
6. 2010 – 59.6 degrees. 
7. 2021 – 59.2 degrees.
8. 2017 – 59.1 degrees.
9. 1950 – 58.9 degrees.
10. 1981 – 58.6 degrees.