Pool swim season in Wilmington, OH
When can you swim in an outdoor pool in Wilmington, OH?
An unheated pool in Wilmington never reaches 78°F in a normal year. It peaks around 76°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 Wilmington
| 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 | $195 | $745 |
| Gas heater + cover | 5 | May to Sep | $290 | $715 |
For a 450 sq ft pool held at 80°F, at OH prices of 18.8¢/kWh electricity and $14/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Wilmington
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 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: NWS Office Wilmington, 0.6 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Wilmington 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° | 1.8 | 31° | 37° | – | – |
| Feb | 42° | 33° | 2.6 | 31° | 37° | – | – |
| Mar | 52° | 42° | 3.6 | 39° | 45° | – | – |
| Apr | 65° | 54° | 4.9 | 50° | 56° | – | – |
| May | 75° | 64° | 5.6 | 61° | 67° | $139 | $202 |
| Jun | 83° | 72° | 6.2 | 71° | 77° | $29 | $47 |
| Jul | 85° | 75° | 6.0 | 76° | 82° | – | – |
| Aug | 84° | 73° | 5.5 | 76° | 82° | – | – |
| Sep | 79° | 67° | 4.6 | 71° | 77° | $27 | $41 |
| Oct | 67° | 56° | 3.2 | 61° | 67° | – | – |
| Nov | 54° | 44° | 2.2 | 49° | 55° | – | – |
| Dec | 43° | 35° | 1.5 | 38° | 44° | – | – |
Heating costs most in May (about $139 with a heat pump, $202 with gas). Sunshine peaks in Jun at 6.2 kWh/m²/day (NASA satellite data, 28.3 km grid cell). Highlighted months are swimmable with no heater.
How Wilmington compares with nearby cities
Wilmington ranks 54 of 176 Ohio cities for unheated swim months; Beavercreek nearby gets a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Xenia, OH | 19 mi | 0 | 5 | $205 |
| Lebanon, OH | 21 mi | 0 | 5 | $233 |
| Washington Court House, OH | 22 mi | 0 | 5 | $257 |
| Centerville, OH | 23 mi | 0 | 5 | $182 |
| Springboro, OH | 24 mi | 0 | 5 | $182 |
| Beavercreek, OH | 25 mi | 1 | 5 | $181 |