Flat Mountain Arm Weather Forecast

    • 33
    • 73

    Areas Smoke

    • 34
    • 70

    Mostly Sunny

    • 41
    • 73

    Slight Chance Thunderstorms

    • 38
    • 68

    Chance Thunderstorms

    • 38
    • 67

    Chance Rain Showers

    • 37
    • 66

    Chance Rain Showers

Today 4 Sep Yellowstone National Park

Mostly sunny. Areas of smoke. Highs in the lower 70s. Northwest Winds 10 to 15 Mph.

Tonight 4 Sep Yellowstone National Park

Mostly clear. Areas of smoke. Lows in the mid 40s.

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  • Temperature Real-Time

Flat Mountain Arm Temperature Statistics

September Temperature

Yellowstone Lake (11.2 miles)

  • Lowest 1 September, 2025

    35.1 °F

  • Average September

    53.9 °F

  • Highest 1 September, 2025

    72 °F

Climate (2020–Present)

Yellowstone Lake (11.2 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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