Lake Merwin Weather Forecast

    • 55
    • 74

    Sunny

    • 53
    • 76

    Mostly Sunny

    • 51
    • 67

    Mostly Sunny

    • 52
    • 70

    Mostly Sunny

    • 53
    • 73

    Mostly Sunny

    • 51
    • 68

    Partly Sunny

    • 51
    • 66

    Partly Sunny

Today 16 Sep South Washington Cascade Foothills

Sunny. Highs in the upper 70s. Winds light.

Tonight 16 Sep South Washington Cascade Foothills

Clear. Lows in the lower 50s. Winds light.

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Lake Merwin Temperature Statistics

September Temperature

Southwest Washington Regional Airport (22.4 miles)

  • Lowest 4 September, 2026

    48 °F

  • Average September

    60.9 °F

  • Highest 9 September, 2026

    86 °F

Climate (2021–2026)

Southwest Washington Regional Airport (22.4 miles)

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  • Average Low 2021–2026

    45.2 °F

  • Average 2021–2026

    53.1 °F

  • Average High 2021–2026

    62.4 °F
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