Grinnell Lake Weather Forecast

    • 41
    • 63

    Increasing Clouds

    • 38
    • 59

    Becoming Sunny

    • 36
    • 59

    Breezy

    • 35
    • 56

    Mostly Sunny

    • 35
    • 57

    Partly Sunny

    • 36
    • 56

    Mostly Sunny

    • 37
    • 56

    Mostly Sunny

Today 10 Sep Upper San Joaquin River

Sunny. A 20 percent chance of Thunderstorms in the afternoon. Highs 64 to 80. Southwest Winds up to 15 Mph.

Tonight 10 Sep Upper San Joaquin River

Partly cloudy. Lows 44 to 56. Southwest Winds up to 10 Mph with Gusts to around 25 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Grinnell Lake Temperature Statistics

September Temperature

Mammoth Yosemite Airport (10.6 miles)

  • Lowest 5 September, 2026

    33.8 °F

  • Average September

    57.7 °F

  • Highest 8 September, 2026

    78.8 °F

Climate (2021–2026)

Mammoth Yosemite Airport (10.6 miles)

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  • Average Low 2021–2026

    29.4 °F

  • Average 2021–2026

    45.7 °F

  • Average High 2021–2026

    60.5 °F
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