Grass Valley Lake Weather Forecast

    • 48
    • 61

    Mostly Sunny

    • 47
    • 59

    Increasing Clouds

    • 45
    • 51

    Rain Showers

    • 44
    • 48

    Rain Showers

    • 42
    • 45

    Rain Showers

    • 36
    • 43

    Rain Showers

    • 36
    • 43

    Chance Rain/Snow

Today 21 Dec San Bernardino County Mountains

Partly cloudy. Highs 55 to 64 above 6000 feet to 61 to 70 below 6000 feet. Areas of Winds southwest 10 to 15 Mph with Gusts to 25 Mph.

Tonight 21 Dec San Bernardino County Mountains

Partly cloudy. Colder. Lows 33 to 43 above 6000 feet to 43 to 53 below 6000 feet. Areas of Winds south 10 Mph.

Graph Plots Open in Graphs

  • Temperature Forecast NOAA

  • Temperature Real-Time

Grass Valley Lake Temperature Statistics

December Temperature

San Bernardino Intl. Airport (11.8 miles)

  • Lowest 4 December, 2025

    40.3 °F

  • Average December

    58.6 °F

  • Highest 10 December, 2025

    87.8 °F

Climate (2020–Present)

San Bernardino Intl. Airport (11.8 miles)

Take a look at our website widgetsAvailable free! Find Out More

  • Average Low 2020–2025

    54.1 °F

  • Average 2020–2025

    63.1 °F

  • Average High 2020–2025

    80.3 °F
Get WillyWeather+ to remove ads