You’ve seen the postcards. Those orange-tinted sunsets, towering saguaro cacti, and people lounging by the pool in mid-winter. It looks like a tropical paradise, right? Well, sort of. If you’re planning a trip, the arizona temperature in december is probably the most misunderstood part of the Southwest experience. People show up in shorts and tank tops only to find themselves shivering at a gas station in the middle of the night.
Arizona isn't just one big sandbox. It's a vertical ladder of climates. While Phoenix might be basking in a gentle 67°F, Flagstaff—just two hours up the road—is likely buried under six inches of fresh powder with temperatures hovering near 15°F.
Honestly, the "dry heat" everyone talks about in the summer becomes a "dry cold" in the winter. Without moisture in the air to hold onto the sun’s warmth, the heat just... vanishes the second the sun dips behind the White Tank Mountains. It’s a wild ride.
The Reality of Arizona Temperature in December
If you’re looking at the averages, the arizona temperature in december across the lower deserts usually sits around a comfortable high of 66°F to 68°F. That sounds like a dream for anyone coming from the Midwest. But those numbers are deceptive.
The diurnal temperature swing in the desert is legendary. It’s not uncommon to see a 30-degree or even 40-degree difference between 2:00 PM and 2:00 AM. In places like Tucson, you might be hiking in a T-shirt at noon, but by the time you’re heading to dinner, you’ll be hunting for a down vest.
Phoenix and the Valley of the Sun
In the Phoenix metro area, December is arguably the best month of the year. The National Weather Service (NWS) data shows an average high of 66°F and an average low of 45°F. However, record highs have hit 78°F or even 80°F on Christmas Day in some years. It’s rare, but it happens. On the flip side, the record low for Phoenix in December is a bone-chilling 22°F.
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Basically, you can’t trust the "average." You have to plan for the extremes.
The High Country: Flagstaff and the Grand Canyon
Think Arizona is all sand? Think again. Flagstaff is one of the snowiest cities in the United States. In December, the average high is a mere 42°F, but the lows frequently drop to 15°F. If a Pacific storm rolls through, the San Francisco Peaks can get slammed with a foot of snow in a single night.
The Grand Canyon’s South Rim follows a similar pattern. It’s beautiful, sure. The red rocks covered in white frost are a photographer’s dream. But the wind chill at the rim can make it feel like 0°F. If you go there expecting "Arizona weather" in the traditional sense, you’re going to have a bad time.
Why the Desert Feels Colder Than It Is
There is a specific phenomenon in the Southwest called "radiative cooling." Because our humidity is so low—often dropping below 20% even in winter—the ground doesn't hold onto heat. As soon as the sun sets, the earth radiates all that energy back into space.
It's a sudden drop. You’ll be walking along, feeling the sun on your back, and then the sun disappears. Suddenly, it feels like someone opened a freezer door.
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Wind is the other factor. The desert is flat, and the wind can whip across the basins with nothing to stop it. A 60°F day with a 15 mph wind feels significantly colder than a 60°F day in a wooded area.
Packing for the "Arizona Layer Cake"
You shouldn't pack a suitcase for December in Arizona; you should pack a toolkit. Because the arizona temperature in december fluctuates so much, your wardrobe needs to be modular.
- The Base: A moisture-wicking T-shirt. Even if it’s 50°F, that desert sun is intense. You will sweat if you're hiking.
- The Insulation: A light fleece or a "puffer" vest. Vests are the secret weapon of Arizonans. They keep your core warm but prevent you from overheating when the sun is out.
- The Shell: A windbreaker or a light denim jacket. This is for the "in-between" times, like 10:00 AM or 4:00 PM.
- The Emergency Kit: A beanie and gloves. If you’re planning on being outdoors after 6:00 PM, you’ll want these. Seriously.
I once saw a guy try to walk around Scottsdale in December wearing nothing but flip-flops and board shorts at 8:00 PM. He looked like he was auditioning for a role as a human popsicle. Don't be that guy.
What to Expect Region by Region
Arizona is basically three different states stacked on top of each other.
- The Low Desert (Yuma, Phoenix): This is your best bet for warmth. Yuma is often the warmest spot in the country during December, regularly hitting the low 70s.
- The Transition Zone (Sedona, Prescott): Sedona is a wild card. You might get a 60°F day or you might get a dusting of snow on the red rocks. Most days hover around 55°F, which is perfect for hiking but too cold for the pool.
- The High Plateau (Flagstaff, Williams, Grand Canyon): This is true winter. Bring the heavy parka, the boots, and the ice scraper for your rental car.
Actionable Tips for Your December Visit
If you want to actually enjoy the arizona temperature in december without a trip to the urgent care for frostbite or heat exhaustion (yes, both are possible), follow these rules:
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Watch the "Dew Point," not just the Temp. In Arizona, the dew point tells you how much moisture is in the air. If it’s very low, expect the temperature to crash the moment the sun sets. If there’s a bit of humidity (maybe a storm is coming), the nights will actually stay warmer.
Check the Elevation.
For every 1,000 feet you climb, the temperature drops about 3.5°F to 5°F. If you’re driving from Phoenix (1,100 ft) to Flagstaff (7,000 ft), you’re looking at a 20-to-30-degree drop just from the drive alone.
Hydrate Like It's July. People forget to drink water in the winter. The air is incredibly dry in December, and you lose moisture through your breath. "Desert skin" is real—bring the heavy-duty lotion and lip balm, or you’ll be peeling by day three.
Book "Heated" Pools.
Just because a hotel has a pool doesn't mean it's swimmable. Unless that water is heated to at least 82°F, the overnight lows will turn it into a polar plunge. Always call ahead and ask if the heat is actually turned on.
Plan Indoor Evenings.
The afternoons are for the trails. The evenings are for the fire pits. Most Arizona resorts have massive outdoor fireplaces for a reason—it's the only way to stay comfortable outside once the stars come out.
The arizona temperature in december is a beautiful, fickle thing. It offers the chance to ski in the morning and play golf in the afternoon, provided you have the right gear in the trunk of your car. Just don't let the sunshine fool you into leaving your jacket at home.