Pool swim season in Lewiston, ID
Swim season in Lewiston without a heater, and with one
An unheated pool in Lewiston 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 Lewiston 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 | $189 | $739 |
| Gas heater + cover | 5 | May to Sep | $215 | $640 |
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 Lewiston
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: Lewiston Airport, 1.7 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Lewiston 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 | 42° | 36° | 1.3 | 34° | 40° | – | – |
| Feb | 47° | 39° | 2.2 | 37° | 43° | – | – |
| Mar | 55° | 45° | 3.3 | 43° | 49° | – | – |
| Apr | 62° | 52° | 4.8 | 50° | 56° | – | – |
| May | 72° | 60° | 6.0 | 59° | 65° | $123 | $136 |
| Jun | 79° | 67° | 6.8 | 67° | 73° | $52 | $62 |
| Jul | 91° | 76° | 7.5 | 76° | 82° | – | – |
| Aug | 90° | 75° | 6.2 | 79° | 85° | – | – |
| Sep | 80° | 66° | 4.5 | 72° | 78° | $14 | $17 |
| Oct | 63° | 53° | 2.8 | 59° | 65° | – | – |
| Nov | 49° | 42° | 1.5 | 46° | 52° | – | – |
| Dec | 41° | 35° | 1.0 | 36° | 42° | – | – |
Heating costs most in May (about $123 with a heat pump, $136 with gas). Sunshine peaks in Jul at 7.5 kWh/m²/day (NASA satellite data, 39.6 km grid cell). Highlighted months are swimmable with no heater.
How Lewiston compares with nearby cities
Lewiston ranks 5 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 |
|---|---|---|---|---|
| Moscow, ID | 23 mi | 0 | 4 | $320 |
| Pullman, WA | 25 mi | 0 | 4 | $274 |
| Walla Walla, WA | 68 mi | 1 | 5 | $187 |
| Cheney, WA | 81 mi | 0 | 4 | $410 |
| Liberty Lake, WA | 88 mi | 0 | 4 | $166 |
| Spokane Valley, WA | 88 mi | 0 | 4 | $166 |