Pool swim season in Walnut Creek, CA
When can you swim in an outdoor pool in Walnut Creek, CA?
An unheated pool in Walnut Creek never reaches 78°F in a normal year. It peaks around 76°F in Aug. The air allows up to 7 swimmable months with a heater (Apr to Oct).
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Heater options for a Walnut Creek pool, side by side
| Option | Months | Swimmable | Energy/yr | All-in/yr |
|---|---|---|---|---|
| No heater | 0 | no month | $0 | $0 |
| Solar cover only | 4 | Jun to Sep | $0 | $50 |
| Solar panels + cover | 6 | May to Oct | $0 | $283 |
| Heat pump + cover | 7 | Apr to Oct | $483 | $1,033 |
| Gas heater + cover | 7 | Apr to Oct | $642 | $1,067 |
For a 450 sq ft pool held at 80°F, at CA prices of 32.6¢/kWh electricity and $22/Mcf gas. All-in spreads the purchase over the equipment's life.
The cheapest way to the full season in Walnut Creek
Solar panels + cover: 6 of 7 possible months for about $283 a year all-in, which works out near $47 for each month it adds.
Before you pay for any heater, buy a solar cover: on its own it adds 4 months 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: Concord Water Treatment Plant, 5.8 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.
Walnut Creek 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 | 58° | 50° | 2.5 | 50° | 56° | – | – |
| Feb | 63° | 54° | 3.4 | 52° | 58° | – | – |
| Mar | 68° | 57° | 4.6 | 57° | 63° | – | – |
| Apr | 72° | 61° | 6.0 | 62° | 68° | $241 | $308 |
| May | 78° | 66° | 6.7 | 67° | 73° | $134 | $183 |
| Jun | 85° | 71° | 7.3 | 72° | 78° | $28 | $41 |
| Jul | 88° | 73° | 6.5 | 76° | 82° | – | – |
| Aug | 88° | 74° | 5.8 | 76° | 82° | – | – |
| Sep | 86° | 72° | 5.1 | 75° | 81° | – | – |
| Oct | 78° | 66° | 4.0 | 70° | 76° | $80 | $110 |
| Nov | 67° | 56° | 2.8 | 61° | 67° | – | – |
| Dec | 59° | 50° | 2.1 | 52° | 58° | – | – |
Heating costs most in Apr (about $241 with a heat pump, $308 with gas). Sunshine peaks in Jun at 7.3 kWh/m²/day (NASA satellite data, 60.3 km grid cell). Highlighted months are swimmable with no heater.
How Walnut Creek compares with nearby cities
Walnut Creek ranks 232 of 376 California cities for unheated swim months, and no nearby city gets a longer unheated season.
| City | Distance | Unheated months | Heat pump months | Heat pump $/yr |
|---|---|---|---|---|
| Pleasant Hill, CA | 4 mi | 0 | 7 | $483 |
| Lafayette, CA | 4 mi | 0 | 7 | $483 |
| Concord, CA | 5 mi | 0 | 7 | $513 |
| Moraga, CA | 6 mi | 0 | 6 | $995 |
| Clayton, CA | 7 mi | 0 | 5 | $245 |
| Orinda, CA | 7 mi | 0 | 6 | $995 |