Boulder Weather Forecast

    • 40
    • 77

    Increasing Clouds

    • 38
    • 61

    Mostly Cloudy

    • 42
    • 63

    Chance Rain

    • 39
    • 62

    Partly Sunny

    • 42
    • 63

    Partly Sunny

    • 40
    • 63

    Partly Sunny

Today 25 Sep Elkhorn and Boulder Mountains

Sunny. Highs 68 to 78. South Winds 5 to 20 Mph. Gusts up to 30 Mph increasing to 40 Mph in the afternoon.

Tonight 25 Sep Elkhorn and Boulder Mountains

Breezy, Colder. Mostly clear. Lows 34 to 42. West Winds 10 to 25 Mph decreasing to 10 to 15 Mph after midnight. Gusts up to 45 Mph.

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Boulder Temperature Statistics

September Temperature

Helena Regional Airport (26.1 miles)

  • Lowest 15 September, 2026

    39.7 °F

  • Average September

    60.9 °F

  • Highest 10 September, 2026

    87.7 °F

Climate (2021–2026)

Helena Regional Airport (26.1 miles)

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  • Average Low 2021–2026

    36.4 °F

  • Average 2021–2026

    47.9 °F

  • Average High 2021–2026

    59.9 °F
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