Treharris Weather Forecast

    • 8
    • 9

    Cloudy

    • 2
    • 8

    Cloudy

    • 1
    • 3

    Cloudy

    • 0
    • 4

    Sunny day

    • 2
    • 3

    Sunny day

    • 3
    • 6

    Cloudy

    • 1
    • 4

    Overcast

Today 22 Dec Wales

A murky start as rain and cloud continue to push northwestwards through the morning. Turning brighter and drier through the afternoon, with some sunny spells possible. Feeling mild for the time of year, with a brisk wind near coasts. Maximum Temperature 10C.

Tonight 22 Dec Wales

Turning increasingly cloudy from the east through the evening, bringing further outbreaks of rain and drizzle overnight, with hill fog possible. Another mild night across the country. Minimum Temperature 5C.

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Treharris Temperature Statistics

December Temperature

St-athan (30km)

  • Lowest 17 December, 2025

    1 °C

  • Average December

    9.4 °C

  • Highest 9 December, 2025

    15.2 °C

Climate (2020–Present)

St-athan (30km)

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  • Average Low 2020–2025

    8.8 °C

  • Average 2020–2025

    11.7 °C

  • Average High 2020–2025

    14.5 °C
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