Lake Mercer Weather Forecast

    • 63
    • 67

    Chance Rain Showers

    • 62
    • 82

    Mostly Sunny

    • 61
    • 87

    Mostly Sunny

    • 60
    • 78

    Partly Sunny

    • 59
    • 76

    Mostly Cloudy

    • 62
    • 80

    Partly Sunny

Today 17 Sep Fairfax

Cloudy with a 50 percent chance of Showers. Highs in the mid 60s. North Winds around 10 Mph with Gusts up to 20 Mph.

Tonight 17 Sep Fairfax

Mostly cloudy. A slight chance of Showers in the evening. Patchy fog. Lows in the lower 60s. North Winds 5 to 10 Mph. Chance of rain 20 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Lake Mercer Temperature Statistics

September Temperature

Fort Belvoir (4.3 miles)

  • Lowest 9 September, 2025

    49.8 °F

  • Average September

    67.9 °F

  • Highest 6 September, 2025

    92.7 °F

Climate (2020–Present)

Fort Belvoir (4.3 miles)

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  • Average Low 2020–2025

    47.8 °F

  • Average 2020–2025

    58.1 °F

  • Average High 2020–2025

    68.3 °F
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