Grinnell Lake Weather Forecast

    • 36
    • 55

    Increasing Clouds

    • 34
    • 50

    Chance Rain/Snow

    • 35
    • 51

    Slight Chance Rain

    • 37
    • 56

    Mostly Sunny

    • 36
    • 56

    Partly Sunny

    • 34
    • 54

    Partly Sunny

Today 20 Sep Upper San Joaquin River

Mostly sunny. Highs 56 to 72. East Winds up to 10 Mph shifting to the southwest in the afternoon.

Tonight 20 Sep Upper San Joaquin River

Mostly cloudy. Lows 39 to 51. West Winds up to 5 Mph with Gusts to around 20 Mph shifting to the northeast after midnight.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Grinnell Lake Temperature Statistics

September Temperature

Mammoth Yosemite Airport (10.6 miles)

  • Lowest 15 September, 2026

    32 °F

  • Average September

    59.4 °F

  • Highest 9 September, 2026

    84.2 °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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