Pool swim season in Hannibal, MO
Hannibal, MO: how long the pool season really is
An unheated pool in Hannibal reaches 78°F in Jul to Aug, about 2 months 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 Hannibal
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 2 | Jul to Aug | $0 | $0 |
| Solar cover only | 3 | Jul to Sep | $0 | $50 |
| Solar panels + cover | 4 | Jun to Sep | $0 | $283 |
| Heat pump + cover | 5 | May to Sep | $136 | $686 |
| Gas heater + cover | 5 | May to Sep | $284 | $709 |
For a 450 sq ft pool held at 80°F, at MO prices of 14.3¢/kWh electricity and $15/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Hannibal
Solar panels + cover: 4 of 5 possible months for about $283 a year all-in, which works out near $142 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: Hannibal Wtr Wks, 1.4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Hannibal 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 | 35° | 26° | 2.0 | 28° | 34° | – | – |
| Feb | 40° | 31° | 2.9 | 28° | 34° | – | – |
| Mar | 51° | 42° | 3.8 | 37° | 43° | – | – |
| Apr | 64° | 53° | 5.0 | 49° | 55° | – | – |
| May | 73° | 64° | 5.7 | 61° | 67° | $109 | $224 |
| Jun | 82° | 73° | 6.4 | 72° | 78° | $18 | $41 |
| Jul | 86° | 77° | 6.4 | 78° | 84° | – | – |
| Aug | 84° | 75° | 5.6 | 78° | 84° | – | – |
| Sep | 78° | 67° | 4.8 | 73° | 79° | $9 | $19 |
| Oct | 66° | 55° | 3.3 | 62° | 68° | – | – |
| Nov | 52° | 43° | 2.3 | 48° | 54° | – | – |
| Dec | 39° | 31° | 1.8 | 36° | 42° | – | – |
Heating costs most in May (about $109 with a heat pump, $224 with gas). Sunshine peaks in Jun at 6.4 kWh/m²/day (NASA satellite data, 25.1 km grid cell). Highlighted months are swimmable with no heater.
How Hannibal compares with nearby cities
Hannibal ranks 75 of 80 Missouri cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Quincy, IL | 15 mi | 2 | 5 | $161 |
| Mexico, MO | 46 mi | 2 | 5 | $116 |
| Troy, MO | 56 mi | 2 | 5 | $118 |
| Moberly, MO | 59 mi | 2 | 5 | $116 |
| Jacksonville, IL | 62 mi | 0 | 5 | $188 |
| Macomb, IL | 65 mi | 0 | 5 | $223 |