Pool swim season in Sunnyside, WA
When can you swim in an outdoor pool in Sunnyside, WA?
An unheated pool in Sunnyside never reaches 78°F in a normal year. It peaks around 74°F in Aug. The air allows up to 5 swimmable months with a heater (May to Sep).
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What each heater buys you in Sunnyside
| 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 | 5 | May to Sep | $312 | $862 |
| Gas heater + cover | 5 | May to Sep | $722 | $1,147 |
For a 450 sq ft pool held at 80°F, at WA prices of 14.4¢/kWh electricity and $18/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Sunnyside
Solar panels + cover: 4 of 5 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 a heat pump sized to your pool's surface area; here it beats gas all-in (heat pump or gas).
Weather station: Sunnyside, 0.6 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Sunnyside 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 | 38° | 30° | 1.3 | 28° | 34° | – | – |
| Feb | 45° | 35° | 2.3 | 32° | 38° | – | – |
| Mar | 55° | 43° | 3.4 | 39° | 45° | – | – |
| Apr | 63° | 49° | 5.0 | 48° | 54° | – | – |
| May | 73° | 58° | 6.0 | 57° | 63° | $157 | $350 |
| Jun | 79° | 64° | 6.8 | 65° | 71° | $75 | $183 |
| Jul | 88° | 71° | 7.5 | 72° | 78° | $14 | $36 |
| Aug | 87° | 69° | 6.3 | 74° | 80° | $3 | $7 |
| Sep | 78° | 61° | 4.6 | 67° | 73° | $63 | $146 |
| Oct | 64° | 49° | 2.8 | 55° | 61° | – | – |
| Nov | 48° | 38° | 1.5 | 42° | 48° | – | – |
| Dec | 37° | 30° | 1.0 | 32° | 38° | – | – |
Heating costs most in May (about $157 with a heat pump, $350 with gas). Sunshine peaks in Jul at 7.5 kWh/m²/day (NASA satellite data, 43.1 km grid cell). Highlighted months are swimmable with no heater.
How Sunnyside compares with nearby cities
Sunnyside ranks 14 of 91 Washington cities for unheated swim months; Kennewick nearby gets a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Grandview, WA | 7 mi | 0 | 5 | $301 |
| West Richland, WA | 29 mi | 0 | 5 | $187 |
| Yakima, WA | 32 mi | 0 | 5 | $205 |
| Richland, WA | 34 mi | 0 | 5 | $187 |
| Kennewick, WA | 40 mi | 1 | 5 | $141 |
| Pasco, WA | 42 mi | 0 | 5 | $190 |