Pool swim season in Boise City, ID
When can you swim in an outdoor pool in Boise City, ID?
An unheated pool in Boise City reaches 78°F in Aug, about 1 month a year. The air allows up to 5 swimmable months with a heater (May to Sep).
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Heater options for a Boise City pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 1 | Aug | $0 | $0 |
| Solar cover only | 3 | Jul to Sep | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 5 | May to Sep | $167 | $717 |
| Gas heater + cover | 5 | May to Sep | $190 | $615 |
For a 450 sq ft pool held at 80°F, at ID prices of 13.0¢/kWh electricity and $8/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Boise City
Solar panels + cover: 4 of 5 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 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: Boise Air Terminal, 2.2 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Boise 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 | 39° | 32° | 1.7 | 31° | 37° | – | – |
| Feb | 46° | 38° | 2.7 | 35° | 41° | – | – |
| Mar | 56° | 45° | 4.0 | 42° | 48° | – | – |
| Apr | 62° | 51° | 5.5 | 51° | 57° | – | – |
| May | 72° | 60° | 6.7 | 59° | 65° | $120 | $133 |
| Jun | 81° | 68° | 7.5 | 68° | 74° | $41 | $50 |
| Jul | 93° | 77° | 7.7 | 77° | 83° | – | – |
| Aug | 91° | 76° | 6.7 | 80° | 86° | – | – |
| Sep | 80° | 66° | 5.2 | 73° | 79° | $6 | $7 |
| Oct | 65° | 53° | 3.5 | 60° | 66° | – | – |
| Nov | 49° | 40° | 2.1 | 46° | 52° | – | – |
| Dec | 39° | 32° | 1.4 | 35° | 41° | – | – |
Heating costs most in May (about $120 with a heat pump, $133 with gas). Sunshine peaks in Jul at 7.7 kWh/m²/day (NASA satellite data, 24.2 km grid cell). Highlighted months are swimmable with no heater.
How Boise City compares with nearby cities
Boise City ranks 1 of 26 Idaho cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Garden City, ID | 6 mi | 0 | 4 | $126 |
| Meridian, ID | 9 mi | 1 | 5 | $167 |
| Kuna, ID | 10 mi | 1 | 5 | $167 |
| Eagle, ID | 11 mi | 1 | 5 | $200 |
| Star, ID | 15 mi | 1 | 5 | $200 |
| Nampa, ID | 17 mi | 1 | 5 | $200 |