Pool swim season in Hermiston, OR
Hermiston, OR: how long the pool season really is
An unheated pool in Hermiston 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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What each heater buys you in Hermiston
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 1 | Aug | $0 | $0 |
| Solar cover only | 2 | Jul to Aug | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 5 | May to Sep | $202 | $752 |
| Gas heater + cover | 5 | May to Sep | $429 | $854 |
For a 450 sq ft pool held at 80°F, at OR prices of 15.5¢/kWh electricity and $17/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Hermiston
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 1 month here for about $50 a year (why a cover comes first). If you get quotes, ask for a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Hermiston Municipal Airport, 1.2 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Hermiston 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 | 43° | 36° | 1.4 | 34° | 40° | – | – |
| Feb | 49° | 39° | 2.3 | 37° | 43° | – | – |
| Mar | 59° | 46° | 3.5 | 43° | 49° | – | – |
| Apr | 67° | 53° | 5.1 | 52° | 58° | – | – |
| May | 76° | 61° | 6.2 | 60° | 66° | $129 | $266 |
| Jun | 82° | 68° | 7.1 | 69° | 75° | $47 | $106 |
| Jul | 93° | 76° | 7.7 | 76° | 82° | – | – |
| Aug | 91° | 74° | 6.5 | 78° | 84° | – | – |
| Sep | 81° | 65° | 4.8 | 71° | 77° | $26 | $57 |
| Oct | 67° | 53° | 3.0 | 59° | 65° | – | – |
| Nov | 51° | 42° | 1.6 | 46° | 52° | – | – |
| Dec | 42° | 35° | 1.1 | 37° | 43° | – | – |
Heating costs most in May (about $129 with a heat pump, $266 with gas). Sunshine peaks in Jul at 7.7 kWh/m²/day (NASA satellite data, 40.6 km grid cell). Highlighted months are swimmable with no heater.
How Hermiston compares with nearby cities
Hermiston ranks 4 of 57 Oregon cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Pendleton, OR | 25 mi | 0 | 5 | $259 |
| Kennewick, WA | 26 mi | 1 | 5 | $141 |
| Pasco, WA | 31 mi | 0 | 5 | $190 |
| Richland, WA | 31 mi | 0 | 5 | $187 |
| West Richland, WA | 34 mi | 0 | 5 | $187 |
| Grandview, WA | 41 mi | 0 | 5 | $301 |