Pool swim season in Belgrade, MT
Swim season in Belgrade without a heater, and with one
An unheated pool in Belgrade never reaches 78°F in a normal year. It peaks around 70°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 Belgrade
| 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 | $329 | $879 |
| Gas heater + cover | 4 | Jun to Sep | $393 | $818 |
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 Belgrade
Gas heater + cover: 4 of 4 possible months for about $818 a year all-in, which works out near $205 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: Bozeman Gallatin Field Airport, 0.9 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Belgrade 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 | 32° | 21° | 1.7 | 20° | 26° | – | – |
| Feb | 36° | 24° | 2.8 | 23° | 29° | – | – |
| Mar | 46° | 34° | 3.8 | 30° | 36° | – | – |
| Apr | 55° | 42° | 4.8 | 40° | 46° | – | – |
| May | 65° | 51° | 5.6 | 49° | 55° | – | – |
| Jun | 74° | 59° | 6.6 | 59° | 65° | $136 | $159 |
| Jul | 85° | 67° | 7.1 | 67° | 73° | $53 | $70 |
| Aug | 84° | 66° | 6.1 | 70° | 76° | $35 | $45 |
| Sep | 73° | 56° | 4.6 | 63° | 69° | $105 | $119 |
| Oct | 58° | 43° | 2.9 | 50° | 56° | – | – |
| Nov | 42° | 30° | 1.8 | 36° | 42° | – | – |
| Dec | 32° | 21° | 1.3 | 24° | 30° | – | – |
Heating costs most in Jun (about $136 with a heat pump, $159 with gas). Sunshine peaks in Jul at 7.1 kWh/m²/day (NASA satellite data, 40.2 km grid cell). Highlighted months are swimmable with no heater.
How Belgrade compares with nearby cities
Belgrade ranks 5 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 |
|---|---|---|---|---|
| Bozeman, MT | 9 mi | 0 | 4 | $336 |
| Helena, MT | 69 mi | 0 | 4 | $223 |
| Butte-Silver Bow, MT | 72 mi | 0 | 3 | $329 |
| Great Falls, MT | 119 mi | 0 | 4 | $220 |
| Billings, MT | 127 mi | 0 | 4 | $142 |
| Cody, WY | 135 mi | 0 | 4 | $212 |