Longmont Weather Forecast

    • 52
    • 75

    Chance Thunderstorms

    • 52
    • 84

    Mostly Sunny

    • 55
    • 84

    Partly Sunny

    • 52
    • 78

    Rain Showers

    • 49
    • 68

    Chance Rain Showers

    • 48
    • 72

    Chance Rain Showers

Today 25 Sep Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County

Mostly cloudy. Patchy fog in the morning. Chance of Thunderstorms in the afternoon. Highs 71 to 77. Chance of precipitation 50 percent.

Tonight 25 Sep Boulder And Jefferson Counties Below 6000 Feet/West Broomfield County

Mostly cloudy with a chance of Showers and slight chance of Thunderstorms in the Evening, then mostly clear after midnight. Lows 48 to 54. Chance of rain 40 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Longmont Temperature Statistics

September Temperature

Vance Brand Airport (3.1 miles)

  • Lowest 22 September, 2026

    45.3 °F

  • Average September

    68.6 °F

  • Highest 13 September, 2026

    93.4 °F

Climate (2021–2026)

Vance Brand Airport (3.1 miles)

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  • Average Low 2021–2026

    38.5 °F

  • Average 2021–2026

    53.4 °F

  • Average High 2021–2026

    68.8 °F
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