Pool swim season in Great Falls, MT
Swim season in Great Falls without a heater, and with one
An unheated pool in Great Falls never reaches 78°F in a normal year. It peaks around 73°F in Aug. The air allows up to 4 swimmable months with a heater (Jun to Sep).
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
What each heater buys you in Great Falls
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 1 | Aug | $0 | $50 |
| Solar panels + cover | 3 | Jun to Aug | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $220 | $770 |
| Gas heater + cover | 4 | Jun to Sep | $270 | $695 |
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 Great Falls
Solar panels + cover: 3 of 4 possible months for about $283 a year all-in, which works out near $94 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 1 month 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: Great Falls 16ST, 1.4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Great Falls 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 | 37° | 27° | 1.5 | 26° | 32° | – | – |
| Feb | 39° | 29° | 2.5 | 28° | 34° | – | – |
| Mar | 48° | 37° | 3.7 | 33° | 39° | – | – |
| Apr | 58° | 46° | 4.8 | 43° | 49° | – | – |
| May | 67° | 54° | 5.8 | 53° | 59° | – | – |
| Jun | 75° | 63° | 6.6 | 62° | 68° | $101 | $124 |
| Jul | 86° | 70° | 7.2 | 71° | 77° | $26 | $35 |
| Aug | 84° | 69° | 5.9 | 73° | 79° | $12 | $16 |
| Sep | 73° | 59° | 4.3 | 65° | 71° | $81 | $95 |
| Oct | 59° | 48° | 2.7 | 53° | 59° | – | – |
| Nov | 45° | 36° | 1.6 | 40° | 46° | – | – |
| Dec | 37° | 28° | 1.2 | 30° | 36° | – | – |
Heating costs most in Jun (about $101 with a heat pump, $124 with gas). Sunshine peaks in Jul at 7.2 kWh/m²/day (NASA satellite data, 15.0 km grid cell). Highlighted months are swimmable with no heater.
How Great Falls compares with nearby cities
Great Falls ranks 3 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 |
|---|---|---|---|---|
| Helena, MT | 71 mi | 0 | 4 | $223 |
| Belgrade, MT | 119 mi | 0 | 4 | $329 |
| Bozeman, MT | 126 mi | 0 | 4 | $336 |
| Butte-Silver Bow, MT | 128 mi | 0 | 3 | $329 |
| Missoula, MT | 135 mi | 0 | 4 | $269 |
| Kalispell, MT | 149 mi | 0 | 4 | $410 |