Pool swim season in Bismarck, ND
When can you swim in an outdoor pool in Bismarck, ND?
An unheated pool in Bismarck never reaches 78°F in a normal year. It peaks around 72°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 Bismarck
| 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 | 3 | Jun to Aug | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $196 | $746 |
| Gas heater + cover | 4 | Jun to Sep | $291 | $716 |
For a 450 sq ft pool held at 80°F, at ND prices of 12.5¢/kWh electricity and $10/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Bismarck
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.
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: Bismarck 2.4 NNW, 1.9 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Bismarck 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 | 22° | 13° | 1.8 | 14° | 20° | – | – |
| Feb | 27° | 17° | 2.9 | 15° | 21° | – | – |
| Mar | 40° | 29° | 3.8 | 24° | 30° | – | – |
| Apr | 54° | 42° | 5.0 | 37° | 43° | – | – |
| May | 66° | 55° | 5.8 | 51° | 57° | – | – |
| Jun | 76° | 64° | 6.5 | 63° | 69° | $82 | $123 |
| Jul | 82° | 70° | 6.8 | 71° | 77° | $22 | $36 |
| Aug | 80° | 68° | 5.6 | 72° | 78° | $18 | $28 |
| Sep | 71° | 59° | 4.3 | 65° | 71° | $74 | $104 |
| Oct | 56° | 45° | 2.7 | 51° | 57° | – | – |
| Nov | 40° | 30° | 1.8 | 36° | 42° | – | – |
| Dec | 27° | 18° | 1.3 | 22° | 28° | – | – |
Heating costs most in Jun (about $82 with a heat pump, $123 with gas). Sunshine peaks in Jul at 6.8 kWh/m²/day (NASA satellite data, 40.5 km grid cell). Highlighted months are swimmable with no heater.
How Bismarck compares with nearby cities
Bismarck ranks 7 of 9 North Dakota cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Mandan, ND | 6 mi | 0 | 4 | $180 |
| Dickinson, ND | 96 mi | 0 | 4 | $222 |
| Jamestown, ND | 98 mi | 0 | 4 | $186 |
| Minot, ND | 101 mi | 0 | 4 | $151 |
| Aberdeen, SD | 144 mi | 0 | 4 | $173 |
| Williston, ND | 165 mi | 0 | 4 | $197 |