Cornerstone Weather Forecast

    • 51
    • 59

    Mostly Cloudy

    • 53
    • 57

    Rain Showers

    • 53
    • 54

    Rain Showers

    • 54
    • 58

    Rain Showers

    • 50
    • 55

    Rain Showers

    • 47
    • 53

    Rain Showers

    • 48
    • 53

    Rain Showers

Today 18 Dec Carquinez Strait and Delta

Widespread fog. Locally dense in the morning. Mostly cloudy. Highs around 58. Light Winds.

Tonight 18 Dec Carquinez Strait and Delta

Mostly cloudy. Patchy fog after midnight. Widespread fog. Locally dense late in the night. A slight chance of rain Showers late in the night. Lows around 49. South Winds up to 10 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Cornerstone Temperature Statistics

December Temperature

Napa, Napa County Airport (7.5 miles)

  • Lowest 2 December, 2025

    37 °F

  • Average December

    44.5 °F

  • Highest 3 December, 2025

    66 °F

Climate (2020–Present)

Napa, Napa County Airport (7.5 miles)

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  • Average Low 2020–2025

    47 °F

  • Average 2020–2025

    58 °F

  • Average High 2020–2025

    70.1 °F
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