Pool swim season in Pontiac, IL
Swim season in Pontiac without a heater, and with one
An unheated pool in Pontiac 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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Heater options for a Pontiac pool, side by side
| 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 | $222 | $772 |
| Gas heater + cover | 5 | May to Sep | $258 | $683 |
For a 450 sq ft pool held at 80°F, at IL prices of 19.2¢/kWh electricity and $11/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Pontiac
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: Pontiac, 0.8 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Pontiac 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 | 32° | 25° | 1.9 | 26° | 32° | – | – |
| Feb | 37° | 29° | 2.7 | 27° | 33° | – | – |
| Mar | 49° | 40° | 3.7 | 35° | 41° | – | – |
| Apr | 63° | 52° | 4.8 | 48° | 54° | – | – |
| May | 74° | 63° | 5.5 | 60° | 66° | $163 | $185 |
| Jun | 82° | 72° | 6.3 | 71° | 77° | $34 | $43 |
| Jul | 84° | 75° | 6.3 | 77° | 83° | – | – |
| Aug | 83° | 73° | 5.6 | 77° | 83° | – | – |
| Sep | 78° | 67° | 4.6 | 72° | 78° | $25 | $30 |
| Oct | 65° | 55° | 3.1 | 61° | 67° | – | – |
| Nov | 50° | 41° | 2.1 | 47° | 53° | – | – |
| Dec | 38° | 30° | 1.6 | 34° | 40° | – | – |
Heating costs most in May (about $163 with a heat pump, $185 with gas). Sunshine peaks in Jul at 6.3 kWh/m²/day (NASA satellite data, 44.9 km grid cell). Highlighted months are swimmable with no heater.
How Pontiac compares with nearby cities
Pontiac ranks 99 of 225 Illinois cities for unheated swim months; Streator nearby gets a longer season without a heater.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Streator, IL | 19 mi | 1 | 5 | $222 |
| Normal, IL | 31 mi | 0 | 5 | $254 |
| Bloomington, IL | 33 mi | 0 | 5 | $254 |
| Ottawa, IL | 33 mi | 0 | 5 | $305 |
| Morris, IL | 36 mi | 0 | 5 | $260 |
| Channahon, IL | 42 mi | 0 | 5 | $267 |