Pool swim season in Williston, ND
Swim season in Williston without a heater, and with one
An unheated pool in Williston 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).
- J
- F
- M
- A
- M
- J
- J
- A
- S
- O
- N
- D
What each heater buys you in Williston
| 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 | $197 | $747 |
| 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 Williston
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: Williston Sloulin Field, 1.2 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Williston 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° | 12° | 1.7 | 13° | 19° | – | – |
| Feb | 27° | 16° | 2.8 | 14° | 20° | – | – |
| Mar | 40° | 29° | 4.0 | 23° | 29° | – | – |
| Apr | 56° | 42° | 4.9 | 38° | 44° | – | – |
| May | 67° | 54° | 5.9 | 51° | 57° | – | – |
| Jun | 77° | 64° | 6.4 | 62° | 68° | $88 | $132 |
| Jul | 85° | 70° | 6.8 | 71° | 77° | $22 | $36 |
| Aug | 84° | 69° | 5.5 | 72° | 78° | $12 | $19 |
| Sep | 73° | 58° | 4.0 | 65° | 71° | $75 | $104 |
| Oct | 56° | 43° | 2.5 | 50° | 56° | – | – |
| Nov | 38° | 28° | 1.5 | 34° | 40° | – | – |
| Dec | 26° | 16° | 1.2 | 20° | 26° | – | – |
Heating costs most in Jun (about $88 with a heat pump, $132 with gas). Sunshine peaks in Jul at 6.8 kWh/m²/day (NASA satellite data, 36.2 km grid cell). Highlighted months are swimmable with no heater.
How Williston compares with nearby cities
Williston ranks 2 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 |
|---|---|---|---|---|
| Dickinson, ND | 98 mi | 0 | 4 | $222 |
| Minot, ND | 109 mi | 0 | 4 | $151 |
| Mandan, ND | 160 mi | 0 | 4 | $180 |
| Bismarck, ND | 165 mi | 0 | 4 | $196 |
| Jamestown, ND | 247 mi | 0 | 4 | $186 |
| Spearfish, SD | 256 mi | 0 | 4 | $198 |