Mount Vernon Weather Forecast

    • 60
    • 81

    Increasing Clouds

    • 67
    • 87

    Becoming Sunny

    • 70
    • 96

    Sunny

    • 70
    • 95

    Mostly Sunny

    • 70
    • 93

    Mostly Sunny

    • 66
    • 92

    Mostly Sunny

    • 63
    • 87

    Mostly Sunny

Today 21 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly sunny. Highs 84 to 88.

Tonight 21 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy. Patchy fog overnight. Cooler. Lows 52 to 60. Areas of Winds west 10 to 15 Mph this evening becoming light.

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Mount Vernon Temperature Statistics

September Temperature

San Bernardino Intl. Airport (4.3 miles)

  • Lowest 19 September, 2026

    57.2 °F

  • Average September

    74.7 °F

  • Highest 9 September, 2026

    105.8 °F

Climate (2021–2026)

San Bernardino Intl. Airport (4.3 miles)

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  • Average Low 2021–2026

    54.2 °F

  • Average 2021–2026

    63.2 °F

  • Average High 2021–2026

    80.3 °F
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