Fortress Mountain Weather Forecast

    • 31
    • 44

    Snow Showers

    • 29
    • 47

    Isolated Thunderstorms

    • 33
    • 46

    Mostly Sunny

    • 37
    • 50

    Partly Sunny

    • 36
    • 48

    Partly Sunny

    • 35
    • 42

    Slight Chance Thunderstorms

Today 16 Sep Absaroka Mountains

Partly cloudy this Morning, then becoming mostly cloudy. Scattered rain Showers. Scattered Thunderstorms this afternoon. Highs around 50. Northeast Winds around 10 Mph with Gusts up to 20 Mph this afternoon. Chance of rain 40 percent.

Tonight 16 Sep Absaroka Mountains

Mostly cloudy in the Evening, then becoming partly cloudy. Scattered rain Showers. Scattered snow Showers with isolated Thunderstorms in the Evening, then isolated snow Showers after midnight. Lows in the mid 30s. Northeast Winds around 10 Mph with Gusts up to 20 Mph in the evening. Chance of precipitation 30 percent.

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Fortress Mountain Temperature Statistics

September Temperature

Yellowstone Lake (33.6 miles)

  • Lowest 6 September, 2025

    30.9 °F

  • Average September

    50.8 °F

  • Highest 3 September, 2025

    75.9 °F

Climate (2020–Present)

Yellowstone Lake (33.6 miles)

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  • Average Low 2020–2025

    22.3 °F

  • Average 2020–2025

    35.2 °F

  • Average High 2020–2025

    48 °F
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