Pool swim season in Rapid City, SD
Rapid City, SD: how long the pool season really is
An unheated pool in Rapid City 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 Rapid City
| 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 | $136 | $686 |
| Gas heater + cover | 4 | Jun to Sep | $185 | $610 |
For a 450 sq ft pool held at 80°F, at SD prices of 14.6¢/kWh electricity and $10/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Rapid City
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: Rapid City NWS Office, 0.4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Rapid City 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° | 26° | 1.9 | 26° | 32° | – | – |
| Feb | 38° | 28° | 2.9 | 27° | 33° | – | – |
| Mar | 47° | 37° | 4.0 | 33° | 39° | – | – |
| Apr | 55° | 45° | 5.0 | 43° | 49° | – | – |
| May | 65° | 55° | 5.9 | 53° | 59° | – | – |
| Jun | 76° | 65° | 6.8 | 64° | 70° | $84 | $115 |
| Jul | 84° | 73° | 7.0 | 73° | 79° | $6 | $9 |
| Aug | 83° | 72° | 6.0 | 75° | 81° | – | – |
| Sep | 74° | 62° | 4.7 | 69° | 75° | $46 | $61 |
| Oct | 59° | 48° | 3.1 | 55° | 61° | – | – |
| Nov | 47° | 37° | 2.1 | 42° | 48° | – | – |
| Dec | 38° | 28° | 1.6 | 31° | 37° | – | – |
Heating costs most in Jun (about $84 with a heat pump, $115 with gas). Sunshine peaks in Jul at 7.0 kWh/m²/day (NASA satellite data, 52.7 km grid cell). Highlighted months are swimmable with no heater.
How Rapid City compares with nearby cities
Rapid City ranks 7 of 14 South 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 |
|---|---|---|---|---|
| Box Elder, SD | 7 mi | 0 | 4 | $160 |
| Spearfish, SD | 41 mi | 0 | 4 | $198 |
| Gillette, WY | 114 mi | 0 | 4 | $166 |
| Pierre, SD | 145 mi | 0 | 4 | $99 |
| Scottsbluff, NE | 154 mi | 0 | 4 | $93 |
| Casper, WY | 177 mi | 0 | 4 | $151 |