Great Falls Weather Forecast

    • 63
    • 89

    Becoming Sunny

    • 67
    • 93

    Mostly Sunny

    • 69
    • 94

    Chance Thunderstorms

    • 68
    • 90

    Slight Chance Thunderstorms

    • 69
    • 91

    Partly Sunny

    • 68
    • 91

    Chance Rain Showers

Today 16 Sep Chester

Mostly sunny. Highs in the upper 80s. Light and variable Winds, becoming east around 5 Mph this afternoon.

Tonight 16 Sep Chester

Clear. Lows in the lower 60s. East Winds around 5 Mph in the Evening, becoming light and variable.

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Great Falls Temperature Statistics

September Temperature

Lancaster County-mc Whirter Field (10.6 miles)

  • Lowest 9 September, 2026

    62.6 °F

  • Average September

    80.6 °F

  • Highest 2 September, 2026

    98.6 °F

Climate (2021–2026)

Lancaster County-mc Whirter Field (10.6 miles)

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  • Average Low 2021–2026

    52.1 °F

  • Average 2021–2026

    62.5 °F

  • Average High 2021–2026

    74 °F
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