| Mon May 20 | Tue May 21 | Wed May 22 | Thu May 23 | |
| Tmin 18-06 |
39°F | 44°F | 39°F | 37°F |
| Tmax 06-18 |
60°F | 60°F | 57°F | 50°F |
| morning 24-06 |
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| a.m. 06-12 |
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| p.m. 12-18 |
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| evening 18-24 |
| Nearby Weather Stations - Merthyr Tydfil | Distance |
| Cardiff Airport | 37.1 km |
| St Athan | 37.4 km |
| Sennybridge | 40.9 km |
| Mumbles | 46.5 km |
| Hereford/Credenhill | 55.1 km |
| Filton | 59.3 km |
| Bristol Airport | 59.5 km |
| Shobdon | 67.0 km |
| Pembrey Burrows | 69.0 km |
| Liscombe | 74.1 km |
| Trawscoed | 79.4 km |
| Royal Marines Base Chivenor | 90.5 km |
| Yeovilton | 96.2 km |
| Dunkeswell Aerodrome | 96.9 km |
| Exeter Airport | 111.4 km |
| Lake Vyrnwy | 113.4 km |