Pool swim season in Iowa City, IA
When can you swim in an outdoor pool in Iowa City, IA?
An unheated pool in Iowa City never reaches 78°F in a normal year. It peaks around 77°F in Jul. The air allows up to 5 swimmable months with a heater (May to Sep).
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What each heater buys you in Iowa City
| 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 | $173 | $723 |
| Gas heater + cover | 5 | May to Sep | $251 | $676 |
For a 450 sq ft pool held at 80°F, at IA prices of 14.6¢/kWh electricity and $11/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Iowa City
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: Iowa City Municipal Airport, 1.3 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Iowa 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 | 31° | 23° | 1.8 | 24° | 30° | – | – |
| Feb | 36° | 27° | 2.9 | 25° | 31° | – | – |
| Mar | 50° | 40° | 3.8 | 34° | 40° | – | – |
| Apr | 63° | 51° | 4.8 | 47° | 53° | – | – |
| May | 73° | 63° | 5.6 | 60° | 66° | $125 | $177 |
| Jun | 83° | 72° | 6.2 | 71° | 77° | $25 | $40 |
| Jul | 86° | 76° | 6.3 | 77° | 83° | – | – |
| Aug | 84° | 74° | 5.5 | 77° | 83° | – | – |
| Sep | 78° | 66° | 4.6 | 71° | 77° | $23 | $34 |
| Oct | 64° | 53° | 3.1 | 60° | 66° | – | – |
| Nov | 49° | 40° | 2.1 | 46° | 52° | – | – |
| Dec | 36° | 28° | 1.5 | 33° | 39° | – | – |
Heating costs most in May (about $125 with a heat pump, $177 with gas). Sunshine peaks in Jul at 6.3 kWh/m²/day (NASA satellite data, 17.5 km grid cell). Highlighted months are swimmable with no heater.
How Iowa City compares with nearby cities
Iowa City ranks 8 of 41 Iowa cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Coralville, IA | 5 mi | 0 | 5 | $173 |
| North Liberty, IA | 7 mi | 0 | 5 | $173 |
| Cedar Rapids, IA | 23 mi | 0 | 5 | $242 |
| Marion, IA | 27 mi | 0 | 5 | $200 |
| Muscatine, IA | 29 mi | 0 | 5 | $185 |
| Davenport, IA | 48 mi | 0 | 5 | $198 |