How extreme does Merthyr Tydfil's weather get?

The hottest, coldest, wettest and snowiest days Merthyr Tydfil has recorded — the outer limits of what its weather can do, and how far they sit beyond a normal day.

Based on 27 years of daily weather observations (1998–present), from the Sheffield City / St Athan station 38 km away. Updated through August 2025 — an all-time extreme only changes when a more extreme day actually occurs, so some dates are old. That is normal, not stale data.

The four kinds of extreme

The hottest, coldest, wettest and snowiest single days Merthyr Tydfil has recorded — each shown against what a normal day that time of year looks like.

🔥 Hottest day

91°F Jul 18, 2022

The three most extreme on record

1 91°F Jul 18, 2022recent

2 90°F Aug 12, 2020

3 90°F Aug 11, 2022

❄️ Coldest night

19°F Jan 4, 2002

The three most extreme on record

1 19°F Jan 4, 2002

2 21°F Dec 20, 1999

3 21°F Jan 17, 2001

In plain terms

Across the record, Merthyr Tydfil has reached as high as 91°F and as low as 19°F. Those are the outer edges worth knowing if you are moving here, planning a trip, or thinking about a house.

Methodology & sources

Temperature & precipitation — 1991–2020 normals computed from 27 years of daily observations at Sennybridge No2, a weather station, about 39 km from the city centre. The underlying daily records come from NOAA's global station network.

How we build these numbers →

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