Most people think of Arizona as a monolith of heat. They picture endless cacti, scorched earth, and a sun that never quits. But honestly, if you're planning to visit in the winter, that mental image is going to get you into trouble. Arizona weather for december is a wild, bipolar experience that can see you shivering in a parka and sweating in a t-shirt within the same 24-hour window.
You've probably heard the term "desert chill." It’s real. While Phoenix might be basking in a comfortable 66°F afternoon, the moment the sun dips behind the White Tank Mountains, the mercury plummets.
The Tale of Two Arizonas
Arizona doesn't have one climate. It has dozens. In the southern half—places like Phoenix, Tucson, and Yuma—December is basically the "Goldilocks" month. It’s the time of year when residents finally stop complaining about the 115-degree summer and start eating every meal on a patio.
But head two hours north?
That's a different world. Flagstaff consistently ranks as one of the snowiest cities in the United States. While Scottsdale is hosting golf tournaments, the San Francisco Peaks are usually buried under a fresh layer of powder. In December 2025, for instance, we saw a massive temperature divide where Phoenix hit a record-breaking warm high while Flagstaff was bracing for a holiday blizzard.
📖 Related: Bryce Canyon National Park: What People Actually Get Wrong About the Hoodoos
Phoenix and the Valley of the Sun
In the Phoenix metro area, the average high in December hangs around 65°F to 67°F.
It sounds perfect. And it is.
But those 45°F nights are what catch tourists off guard. You’ll see locals in heavy puffy jackets while tourists from Minnesota are walking around in shorts. Honestly, the dry air makes the cold feel sharper. It cuts through thin fabrics.
- Average Highs: 66°F
- Average Lows: 45°F
- Rainfall: About 1.0 inch (usually delivered in one or two gray, drizzly days)
High Country Realities
If you are heading to the Grand Canyon or Flagstaff, don't let the "Arizona" label fool you. Elevation is everything here. Flagstaff sits at roughly 7,000 feet. The Grand Canyon's South Rim is similar.
December weather there is legit winter. You’re looking at daytime highs that struggle to reach 40°F and nights that routinely drop into the teens. In late December 2025, several storms dumped significant snow across the I-40 corridor, making travel between Williams and Flagstaff a bit of a nightmare for those without four-wheel drive.
The Surprise of Winter Rain and "Inside Sliders"
Arizona weather for december is heavily influenced by the Pacific. Specifically, we look at El Niño and La Niña cycles. We just wrapped up a year where a weak La Niña was expected to keep us bone-dry, but the desert has a way of surprising you.
👉 See also: Getting to Burning Man: What You Actually Need to Know About the Journey
Meteorologists often talk about "inside sliders."
These are storm systems that drop down from the north through the Great Basin rather than coming off the coast. They don't bring much moisture, but they bring a "blue northie" wind that can make a 60-degree day feel like 40.
Why Does it Rain in the Desert?
December is actually one of the wetter months for the state, though "wet" is a relative term. Unlike the summer monsoons—which are violent, localized, and fast—winter rains in Arizona are typically widespread and gentle. They can last for 12 hours. It’s a soaking rain that turns the desert floor a vibrant, almost neon green by January.
The Arizona Weather for December Packing Strategy
I’ve seen it a thousand times: someone lands at Sky Harbor in a tank top and has to buy a $60 sweatshirt at the airport gift shop by 6:00 PM.
Layering isn't a suggestion; it's a survival tactic. Start with a base layer. Add a light sweater. Finish with a wind-resistant shell. If you're doing the "Rim to Lowland" drive—going from the Grand Canyon down to Phoenix—you will experience a 30-degree temperature swing in less than three hours. It’s like traveling from Canada to Mexico in one afternoon.
✨ Don't miss: Tiempo en East Hampton NY: What the Forecast Won't Tell You About Your Trip
- Sunscreen: The UV index remains high even when it's cool. The thin air in the high country means you’ll burn faster in the snow than you would on a beach.
- Moisturizer: The humidity in December often hovers around 20-30%. Your skin will feel like parchment paper within two days if you don't hydrate and lotion up.
- Footwear: If you're hiking, remember that desert trails are rocky and hold cold. If you're in the north, waterproof boots are mandatory for the slush.
Looking Back at December 2025
This past year was a bit of an anomaly. Phoenix recorded its hottest December on record, with temperatures staying roughly seven degrees above the historical normal. We saw more 75-degree days than usual, which kept the patio heaters off but raised a lot of concerns about the ongoing drought.
Tucson also saw a weirdly dry stretch, setting records for low dew points in late December. When the air is that dry, the temperature swings are even more violent. On December 23, the airport recorded a low of 24°F, only to bounce back into the 70s a couple of days later.
Actionable Tips for Your Visit
If you want to master Arizona weather for december, stop checking the "state" forecast and start checking specific elevations.
- Check the "Area Forecast Discussion": If you really want to know what's happening, go to the National Weather Service website for Phoenix or Flagstaff and read the "Forecast Discussion." It’s written by local meteorologists for pilots and hobbyists, and it gives you the "why" behind the "what."
- Monitor I-17 Conditions: This is the main artery between the desert and the mountains. In December, a sudden snow squall near Sunset Point can shut the whole highway down. Download the ADOT (Arizona Department of Transportation) app before you leave.
- Plan for Early Sunsets: The sun disappears behind the mountains early here. By 5:15 PM, it’s dark. The temperature drop starts the second the sun vanishes, so don't be caught on a trail at 4:30 PM in just a t-shirt.
If you're coming for the warmth, stick to the valley floor. If you're coming for the holidays, head north, but bring the heavy wool. Arizona in December is a choose-your-own-adventure climate, and as long as you respect the elevation, it’s easily the best time of year to be in the Southwest.
Pack a mix of light and heavy clothes, keep a gallon of water in your rental car regardless of the temperature, and always keep a pair of sunglasses on the dashboard. The winter sun sits low on the horizon and can be blinding during your morning and evening commutes. By staying flexible with your itinerary and your wardrobe, you can navigate the extremes of the desert winter like a local.