Updated: June 4, 2026
Are you building a pool in Arizona? Do you really need a heater? It's 110 degrees in July. Shouldn't the pool heat itself.
Can you swim in Arizona when the weather gets cold? What is the difference between swimming in March and October?
This article offers how cold an unheated pool water gets in Phoenix across the year. We share who needs a heater and who doesn't. Plus, we take a look at how comfortable a heater makes your pool in the coldest months.
How Cold Does an Unheated Pool Get in Phoenix?
Most unheated pools in Phoenix average between 55–60°F in December and January. Now, you have a cold plunge than a swimming pool. The average person stops swimming comfortably anywhere below 70°F. Phoenix pool water doesn't consistently reach that on its own until late April.
Pool water temperature in a low-humidity desert climate tracks closely with the average of the daily high and low. Plus or minus about 10 degrees. In January, Phoenix averages a high of 67°F and a low of 44°F.
What that means for your swim season without a heater:
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Comfortable swimming in Phoenix runs roughly late April through early October
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October water is swimmable for some, borderline for most families with young kids
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November through March, most Phoenix homeowners are not in the pool
Can We Swim All Year Round
"A lot of people move to Arizona and they think they're gonna swim all year round. A question I always ask people is, do you know what the swim season is? And they're like, oh yeah, we can swim all year round. But really we start swimming usually sometime in May and we quit swimming sometime in September. So October, when the weather is beautiful outside and we're outside barbecuing, the water's just too cold." — Gary Dudley, Pool Designer Shasta Pools (30+ years)
Will a Heater Make Your Pool Warm Enough to Swim and Does It Work in November and January
Yes, heat pump will get your pool to a comfortable swimming temperature and keep it there through most of the Arizona winter. Most homeowners who heat their pools target around 87–88°F. A heat pump gets there reliably as long as the daytime high reaches 55°F or above.
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October through April: A heat pump runs efficiently and keeps the pool at your target temperature.
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November, December, January: These are Phoenix's coldest months. The heat pump still works on most days because daytime highs usually stay above 55°F. There are roughly five to ten days per year where daytime temperatures stay too low for the heat pump to reach 87–88°F efficiently.
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Those coldest days: If it is genuinely too cold outside for the heat pump to do its job fully, it is almost certainly too cold to swim anyway.
Use Heat Pump October through April
"You'll use a heat pump probably more like the beginning of October to like the end of April. And where you'll see a really big effect on it is during November, December, January — those are our coldest months. And those might be the few days it won't work. And typically when it's that cold outside, you're not going to swim in it anyway." — Gary Dudley, Pool Designer Shasta Pools
Can You Swim in an Arizona Pool Year-Round Without a Heater?
How warm is pool water naturally in summer months?
In the summer, your pool water often reaches 85–95°F, sometimes even warmer. It’s perfect for swimming without needing a heater.
What happens to pool water temperature in fall, winter, and spring?
When cooler nights return in October, pool water starts to dip into the 60s and low 70s. By December and January, most unheated pools in Phoenix are 50–60°F—way too cold for most swimmers.
Are Arizona winters mild enough for year-round swimming without heat?
Arizona winters are mild compared to other states, but “mild” doesn’t mean “swim-ready.” Unless you love polar plunges, most families stop swimming once water temps drop below 70°F.
What Is the Average Pool Water Temperature by Season in Arizona?
What’s the average pool water temperature in summer?
June–September: 85–95°F— no heater needed.
How cold does pool water get in winter months (Phoenix vs. Tucson vs. northern AZ)?
Pool water in AZ typically balances out to whatever the overnight low is...assuming a consistent overnight low temperature for two to three days.
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Phoenix/Tucson: low 50s in winter
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Northern Arizona: even cooler—sometimes down into the low 40s
When do most Arizona homeowners stop using their pools without a heater?
Most families stop regular swimming in October and don’t jump back in until late May without a heater. Having a heated pool can add 3–5 extra months of comfortable swimming each year.
Does having a heated pool increase home value or rental appeal?
Yes-ish, Heated pools are attractive to buyers and renters who want year-round fun. Renting a home in AZ during Spring baseball in March is the absolute best, perfect weather, 15 Major League Baseball teams to choose from...but a bit of a "strikeout" if the pool isn't heated.
What Types of Pool Heaters Work Best in Arizona?
What’s the difference between gas, electric, and heat pumps in Arizona’s climate?
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Gas heaters: Fast heat, great for spas.
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Electric heat pumps: Use Arizona’s warm air, very efficient most of the year.
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Electric resistance heaters: Rarely used—too costly here.
- Heat Pump: The most effective option to heat your pool.
Is solar pool heating effective in Arizona?
Yes, it certainly can be. As long as there are no clouds around, which isn't often in AZ, solar heating is an effective and eco-friendly option.
Which heater type saves the most money long-term in Arizona?
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Best for quick heating: Gas
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Best for efficiency: Heat pump
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Best for savings: Solar (low monthly cost after install - installation price is the highest)
How Much Does It Cost to Heat a Pool in Arizona Each Month?
What’s the monthly cost of running a gas heater in Arizona?
Gas heaters typically cost around $300–$500 per month, assuming you're heating the pool every weekend during the Fall and Winter months, but if you plan on using it more than just the weekends, that can rise much higher with heavy use.
The difference in cost often depends on whether you’re heating just your pool, just your spa, or both — and yes, if you didn’t know, it’s absolutely possible to heat either one separately or both together. The Attendant makes managing that simple, giving you full control over how and when each is heated.
How much does a heat pump or solar system cost to operate per month?
A heat pump typically costs around $50–$150 per month to operate, depending on the size of your pool, your preferred water temperature, and how often it runs. That average price of $50-$150 per month should give you the ability to swim every day of the month of March vs only the weekends compared to the same cost of a gas heater.
A solar system, on the other hand, is virtually free to operate once installed, aside from minimal energy costs to run the circulation pump. While solar heating relies on sunlight availability, it’s one of the most sustainable ways to keep your pool comfortable. Just be sure to check your HOA if they allow them in your community and with your local fire department if they are willing to get on the roof, if they are installed. Some Arizona fire departments have adopted a policy that they will not get on a roof that has solar panels because of the danger to the fire fighter.
And just like with gas heaters, you can choose to heat just your pool, just your spa, or both.
How do pool covers reduce monthly heating bills?
A pool cover can reduce heat loss by 45%-55%, saving most homeowners $50–$100 per month on heating costs. By preventing evaporation — the biggest source of heat loss — covers help your pool retain warmth overnight and on cooler days.
Beyond energy savings, a good cover also keeps debris out and reduces chemical use, making your pool more efficient and easier to maintain overall.
Do All Pools in Arizona Need Heaters, or Only Certain Ones?
Do pool size, depth, and sunlight affect how much heating you need?
Absolutely. Smaller or shallower pools naturally warm up faster and retain heat more easily, which means they often don’t require as much heating as larger, deeper pools.
Sun exposure plays a big role, too. Pools in sunny backyards tend to stay warmer throughout the day, while those in shaded areas or surrounded by trees may lose heat more quickly and rely more on heaters to maintain a comfortable temperature.
What Are the Alternatives to Installing a Heater in Arizona?
Do solar covers, liquid blankets, or darker pool finishes really keep the water warm?
Yes — solar pool covers or blankets are one of the most effective passive heating options. They trap the sun’s warmth, reduce evaporation, and can extend your swim season by several weeks.
Liquid solar covers can also help minimize evaporation, which saves water and heat loss, but in Arizona’s intense sun and wind, they’re MUCH less effective than physical covers.
Many assume that a black or darker pool finishes will absorb and retain warmth. While this is technically true, its safe to assume that you might gain 2-4°F in temperature.
How Do You Decide if a Pool Heater Is Worth It in Arizona?
It really comes down to how often you want to swim, how much you entertain and how much comfort you expect from your pool.
If you’d like to swim 10–12 months a year, a heater is absolutely worth the investment. But if you’re comfortable enjoying your pool for 4–5.5 months, you may be fine without one.
Also consider your budget — pool heaters typically cost $3,000–$7,000 to install, plus ongoing monthly energy costs. Still, for many homeowners, the added warmth, comfort for kids and guests, and the ability to entertain year-round make it an easy “yes.”
Ask yourself this question, "Do I feel like my pool is a better investment if I use it year-round or half the year?" Your answer to this will tell you if a heater is a worthwhile investment for you or not.
Should Arizona Homeowners Invest in a Pool Heater?
Here’s the simple truth:
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Without a heater, you’ll enjoy your pool 4–5.5 months a year.
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With a heater, you can extend that to 10–12 months of fun.
The decision comes down to comfort, lifestyle, and budget. If you want year-round swimming, invest in a heater. If you’re happy with seasonal fun, you may not need one.
At Shasta, we help Arizona homeowners make the right call—whether that’s installing a heater or showing you how to get the most out of your pool without one.
Want to know if a heater is right for you?
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Schedule a free consultation with our team.
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Download our Arizona Pool Heating Guide: Costs, Options, and Savings.
We’ll give you the real numbers and help you make the decision that keeps your pool fun—and your wallet happy.
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