Pool swim season in Billings, MT
When can you swim in an outdoor pool in Billings, MT?
An unheated pool in Billings never reaches 78°F in a normal year. It peaks around 75°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 Billings
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 2 | Jul to Aug | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $142 | $692 |
| Gas heater + cover | 4 | Jun to Sep | $178 | $603 |
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 Billings
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.
Before you pay for any heater, buy a solar cover: on its own it adds 2 months here for about $50 a year (why a cover comes first). 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: Billings International Airport, 1.3 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Billings 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 | 36° | 27° | 1.8 | 26° | 32° | – | – |
| Feb | 39° | 29° | 2.8 | 28° | 34° | – | – |
| Mar | 49° | 38° | 3.8 | 35° | 41° | – | – |
| Apr | 57° | 46° | 4.7 | 44° | 50° | – | – |
| May | 67° | 55° | 5.7 | 53° | 59° | – | – |
| Jun | 77° | 65° | 6.7 | 64° | 70° | $84 | $107 |
| Jul | 87° | 73° | 7.1 | 73° | 79° | $7 | $9 |
| Aug | 86° | 72° | 6.0 | 75° | 81° | – | – |
| Sep | 74° | 61° | 4.6 | 68° | 74° | $51 | $62 |
| Oct | 59° | 48° | 2.9 | 55° | 61° | – | – |
| Nov | 46° | 36° | 1.9 | 41° | 47° | – | – |
| Dec | 36° | 28° | 1.4 | 30° | 36° | – | – |
Heating costs most in Jun (about $84 with a heat pump, $107 with gas). Sunshine peaks in Jul at 7.1 kWh/m²/day (NASA satellite data, 32.3 km grid cell). Highlighted months are swimmable with no heater.
How Billings compares with nearby cities
Billings ranks 1 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 |
|---|---|---|---|---|
| Cody, WY | 91 mi | 0 | 4 | $212 |
| Sheridan, WY | 103 mi | 0 | 4 | $216 |
| Bozeman, MT | 121 mi | 0 | 4 | $336 |
| Belgrade, MT | 127 mi | 0 | 4 | $329 |
| Helena, MT | 175 mi | 0 | 4 | $223 |
| Great Falls, MT | 176 mi | 0 | 4 | $220 |