Cosmopolis Weather Forecast

    • 44
    • 63

    Mostly Cloudy

    • 44
    • 65

    Becoming Sunny

    • 53
    • 63

    Mostly Cloudy

    • 50
    • 61

    Rain

    • 49
    • 64

    Mostly Cloudy

    • 48
    • 64

    Mostly Cloudy

    • 47
    • 64

    Partly Sunny

Today 26 Sep Lower Chehalis River Valley

Mostly sunny. Highs in the mid 60s to lower 70s.

Tonight 26 Sep Lower Chehalis River Valley

Partly cloudy in the evening then becoming mostly cloudy. Lows in the lower to mid 40s. Northeast wind to 10 Mph in the evening becoming light.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Cosmopolis Temperature Statistics

September Temperature

Hoquiam, Bowerman Airport (6.8 miles)

  • Lowest 20 September, 2026

    46.7 °F

  • Average September

    60 °F

  • Highest 17 September, 2026

    76.6 °F

Climate (2021–2026)

Hoquiam, Bowerman Airport (6.8 miles)

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  • Average Low 2021–2026

    46.3 °F

  • Average 2021–2026

    52.4 °F

  • Average High 2021–2026

    58.6 °F
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