Pool swim season in Flagstaff, AZ
When can you swim in an outdoor pool in Flagstaff, AZ?
An unheated pool in Flagstaff never reaches 78°F in a normal year. It peaks around 69°F in Aug. The air allows up to 4 swimmable months with a heater (Jun to Sep).
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What each heater buys you in Flagstaff
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 0 | no month | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $308 | $858 |
| Gas heater + cover | 4 | Jun to Sep | $715 | $1,140 |
For a 450 sq ft pool held at 80°F, at AZ prices of 15.4¢/kWh electricity and $19/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Flagstaff
Solar panels + cover: 4 of 4 possible months for about $283 a year all-in, which works out near $71 for each month it adds.
A solar cover alone adds no swim months here, so if you want a longer season you need a heater (why); still use one at night to hold the heat you pay for. If you get quotes, ask for a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Flagstaff Airport, 3.8 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Flagstaff month by month: air, sun and pool water
| Month | Air high | Air avg | Sun kWh/m²/day | Water, unheated | Water, covered | Heat pump $ | Gas $ |
|---|---|---|---|---|---|---|---|
| Jan | 43° | 31° | 3.2 | 30° | 36° | – | – |
| Feb | 46° | 33° | 4.2 | 33° | 39° | – | – |
| Mar | 52° | 38° | 5.7 | 38° | 44° | – | – |
| Apr | 59° | 44° | 7.0 | 45° | 51° | – | – |
| May | 68° | 51° | 7.8 | 52° | 58° | – | – |
| Jun | 79° | 61° | 8.4 | 62° | 68° | $118 | $270 |
| Jul | 82° | 67° | 6.9 | 68° | 74° | $55 | $137 |
| Aug | 79° | 65° | 6.4 | 69° | 75° | $43 | $104 |
| Sep | 74° | 58° | 5.9 | 65° | 71° | $92 | $204 |
| Oct | 64° | 48° | 4.8 | 55° | 61° | – | – |
| Nov | 52° | 38° | 3.6 | 43° | 49° | – | – |
| Dec | 43° | 30° | 2.8 | 34° | 40° | – | – |
Heating costs most in Jun (about $118 with a heat pump, $270 with gas). Sunshine peaks in Jun at 8.4 kWh/m²/day (NASA satellite data, 36.7 km grid cell). Highlighted months are swimmable with no heater.
How Flagstaff compares with nearby cities
Flagstaff ranks 44 of 44 Arizona cities for unheated swim months; Cottonwood, Camp Verde, Chino Valley nearby get a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Cottonwood, AZ | 36 mi | 4 | 9 | $519 |
| Camp Verde, AZ | 45 mi | 3 | 8 | $433 |
| Chino Valley, AZ | 54 mi | 2 | 7 | $378 |
| Prescott Valley, AZ | 57 mi | 1 | 6 | $249 |
| Prescott, AZ | 62 mi | 1 | 6 | $249 |
| Payson, AZ | 67 mi | 1 | 7 | $406 |