Pool swim season in Grass Valley, CA

When can you swim in an outdoor pool in Grass Valley, CA?

An unheated pool in Grass Valley never reaches 78°F in a normal year. It peaks around 77°F in Aug. The air allows up to 6 swimmable months with a heater (May to Oct).

1. J
2. F
3. M
4. A
5. M
6. J
7. J
8. A
9. S
10. O
11. N
12. D

What each heater buys you in Grass Valley

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 Grass Valley

Heat pump + cover: 6 of 6 possible months for about $1,200 a year all-in, which works out near $200 for each month it adds.

Before you pay for any heater, buy a solar cover: on its own it adds 3 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: Grass Valley #2, 1.4 mi away (NOAA 1991–2020 normals). Water temperature is estimated from air and sunshine, not measured.

Grass Valley month by month: air, sun and pool water

Heating costs most in May (about $300 with a heat pump, $373 with gas). Sunshine peaks in Jul at 8.3 kWh/m²/day (NASA satellite data, 49.5 km grid cell). Highlighted months are swimmable with no heater.

How Grass Valley compares with nearby cities

Grass Valley ranks 218 of 376 California cities for unheated swim months; Auburn, Lincoln, Marysville nearby get a longer season without a heater.