Pool swim season in Missoula, MT
Missoula, MT: how long the pool season really is
An unheated pool in Missoula never reaches 78°F in a normal year. It peaks around 71°F in Aug. The air allows up to 4 swimmable months with a heater (Jun to Sep).
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Heater options for a Missoula pool, side by side
| 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 | 2 | Jul to Aug | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $269 | $819 |
| Gas heater + cover | 4 | Jun to Sep | $328 | $753 |
For a 450 sq ft pool held at 80°F, at MT prices of 14.1¢/kWh electricity and $9/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Missoula
Gas heater + cover: 4 of 4 possible months for about $753 a year all-in, which works out near $188 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 gas as well as a heat pump: once the purchase price is counted, gas comes out cheaper all-in here (heat pump or gas).
Weather station: Missoula 2 NE, 3.2 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Missoula 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 | 34° | 27° | 1.3 | 25° | 31° | – | – |
| Feb | 39° | 31° | 2.0 | 28° | 34° | – | – |
| Mar | 49° | 38° | 3.1 | 35° | 41° | – | – |
| Apr | 57° | 45° | 4.4 | 43° | 49° | – | – |
| May | 67° | 54° | 5.6 | 52° | 58° | – | – |
| Jun | 73° | 60° | 6.4 | 60° | 66° | $120 | $144 |
| Jul | 85° | 69° | 7.4 | 69° | 75° | $40 | $54 |
| Aug | 84° | 68° | 6.2 | 71° | 77° | $22 | $29 |
| Sep | 73° | 58° | 4.4 | 64° | 70° | $87 | $101 |
| Oct | 57° | 45° | 2.6 | 51° | 57° | – | – |
| Nov | 41° | 34° | 1.4 | 38° | 44° | – | – |
| Dec | 33° | 26° | 1.0 | 28° | 34° | – | – |
Heating costs most in Jun (about $120 with a heat pump, $144 with gas). Sunshine peaks in Jul at 7.4 kWh/m²/day (NASA satellite data, 55.1 km grid cell). Highlighted months are swimmable with no heater.
How Missoula compares with nearby cities
Missoula ranks 4 of 8 Montana cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Kalispell, MT | 94 mi | 0 | 4 | $410 |
| Butte-Silver Bow, MT | 94 mi | 0 | 3 | $329 |
| Helena, MT | 97 mi | 0 | 4 | $223 |
| Great Falls, MT | 135 mi | 0 | 4 | $220 |
| Moscow, ID | 141 mi | 0 | 4 | $320 |
| Coeur d'Alene, ID | 142 mi | 0 | 4 | $190 |