Pool swim season in Marshfield, WI
When can you swim in an outdoor pool in Marshfield, WI?
An unheated pool in Marshfield never reaches 78°F in a normal year. It peaks around 70°F in Aug. The air allows up to 4 swimmable months with a heater (Jun to Sep).
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What each heater buys you in Marshfield
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 0 | no month | $0 | $50 |
| Solar panels + cover | 3 | Jun to Aug | $0 | $283 |
| Heat pump + cover | 4 | Jun to Sep | $305 | $855 |
| Gas heater + cover | 4 | Jun to Sep | $340 | $765 |
For a 450 sq ft pool held at 80°F, at WI prices of 19.1¢/kWh electricity and $11/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Marshfield
Solar panels + cover: 3 of 4 possible months for about $283 a year all-in, which works out near $94 for each month it adds.
A solar cover alone adds no swim months here, so if you want a longer season you need a heater (why); still use one at night to hold the heat you pay for. 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: Marshfield Municipal Airport, 1.9 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Marshfield 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 | 23° | 15° | 1.8 | 17° | 23° | – | – |
| Feb | 27° | 19° | 3.0 | 17° | 23° | – | – |
| Mar | 39° | 30° | 4.0 | 26° | 32° | – | – |
| Apr | 54° | 44° | 4.6 | 39° | 45° | – | – |
| May | 67° | 56° | 5.5 | 52° | 58° | – | – |
| Jun | 76° | 65° | 6.0 | 64° | 70° | $114 | $129 |
| Jul | 80° | 69° | 6.2 | 70° | 76° | $38 | $46 |
| Aug | 78° | 67° | 5.2 | 70° | 76° | $38 | $45 |
| Sep | 70° | 59° | 4.1 | 64° | 70° | $115 | $120 |
| Oct | 56° | 47° | 2.6 | 53° | 59° | – | – |
| Nov | 41° | 33° | 1.7 | 39° | 45° | – | – |
| Dec | 28° | 21° | 1.3 | 25° | 31° | – | – |
Heating costs most in Sep (about $115 with a heat pump, $120 with gas). Sunshine peaks in Jul at 6.2 kWh/m²/day (NASA satellite data, 31.7 km grid cell). Highlighted months are swimmable with no heater.
How Marshfield compares with nearby cities
Marshfield ranks 96 of 98 Wisconsin cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Wisconsin Rapids, WI | 25 mi | 0 | 4 | $284 |
| Stevens Point, WI | 32 mi | 0 | 4 | $281 |
| Wausau, WI | 33 mi | 0 | 3 | $183 |
| Plover, WI | 34 mi | 0 | 4 | $281 |
| Weston, WI | 34 mi | 0 | 3 | $183 |
| Chippewa Falls, WI | 63 mi | 0 | 4 | $217 |