Hardly any UK towns collect more rain than Ystradgynlais: 1,923 mm (76 in) a year
Midsummer highs settle at about 20.3°C (69°F). None of the 7 Powys towns has milder January nights. Expect the heaviest rain in December and the lightest in April. Garden chairs stay out from June to September, the months with highs of 18–20°C.
Met Office 1991–2020 averages for the town itself.
A year in Ystradgynlais at a glance
Each month’s typical high and low, in °C.
What a year in Ystradgynlais feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,923 mm of rain a year
December is the wettest month and April the driest. About 65 days a year bring 10 mm (0.4 in) or more. The wettest of 7 Powys towns of 2,500+.
Rain by month
Millimetres
38 air frosts and 8 days of 25°C a year
On about 38 nights a year the air drops below freezing, and on about under 1 days it stays below freezing all day. About 8 days a year reach 25°C (77°F).
Day counts are 1991–2020 averages from the Met Office’s 2 km grid. The Met Office calls a day of 25°C or more a summer day and a night below 0°C an air frost; ground frosts, on grass, come more often.
The Met Office station at Cardiff Bute Park
Cardiff Bute Park is 32 miles south-east of Ystradgynlais, 9 m (30 ft) above sea level. It is the nearest of the 37 long-running stations the Met Office publishes in full; at that distance read it for sunshine and the station’s own record, not as the town’s figures.
| Month | High | Low | Rain | Air frosts |
|---|---|---|---|---|
| January | 8.6°C | 2.5°C | 127 mm | 8.1 |
| February | 9.1°C | 2.5°C | 93 mm | 7.5 |
| March | 11.3°C | 3.9°C | 85 mm | 3.9 |
| April | 14.4°C | 5.7°C | 72 mm | 1.4 |
| May | 17.4°C | 8.5°C | 78 mm | 0.0 |
| June | 20.1°C | 11.3°C | 73 mm | 0.0 |
| July | 21.8°C | 13.1°C | 84 mm | 0.0 |
| August | 21.4°C | 12.9°C | 105 mm | 0.0 |
| September | 19.1°C | 10.7°C | 87 mm | 0.0 |
| October | 15.2°C | 8.0°C | 128 mm | 1.0 |
| November | 11.6°C | 4.9°C | 131 mm | 3.7 |
| December | 9.1°C | 2.9°C | 140 mm | 8.3 |
| Year | 14.9°C | 7.2°C | 1,201 mm | 34 |
Met Office historic station data, Cardiff Bute Park, 1991–2020 months averaged (a month needs 20 of the 30 years; estimated values counted, missing months left out). Sunshine: Campbell-Stokes recorder.
How Ystradgynlais compares
Against the 2,537 towns and cities of 2,500 or more across the UK, each with its own Met Office averages, and its place among Powys towns that size.
Nearby towns’ climate
The nearest towns of 1,000+ within 12 miles: a hill, a valley or the sea can make a real difference over a few miles.
| Town | July high | January low | Rain a year |
|---|---|---|---|
| Ystradgynlais | 20.3°C | 2.2°C | 1,923 mm |
| Ystalyfera 1.9 mi | 20.3°C about the same | 2.2°C about the same | 1,920 mm |
| Seven Sisters 2.0 mi | 20.2°C about the same | 1.9°C about the same | 1,921 mm |
| Cwmllynfell and Ystradowen 3.1 mi | 20.1°C about the same | 2.2°C about the same | 1,997 mm |
| Creunant 3.5 mi | 19.8°C about the same | 2.0°C about the same | 1,868 mm |
| Gwaun-Cae-Gurwen 5.4 mi | 19.9°C about the same | 2.1°C about the same | 1,720 mm |
| Brynamman 5.4 mi | 19.9°C about the same | 2.1°C about the same | 1,716 mm |
Ystradgynlais weather by month
Average daily high and low, mean temperature and rain, 1991–2020, for the town itself (the Met Office’s HadUK-Grid).
| Month | High | Low | Mean | Rain |
|---|---|---|---|---|
| January | 7.7°C 46°F | 2.2°C 36°F | 5.0°C | 214 mm 8.4 in |
| February | 8.0°C 46°F | 2.0°C 36°F | 5.0°C | 161 mm 6.3 in |
| March | 10.0°C 50°F | 3.1°C 38°F | 6.6°C | 137 mm 5.4 in |
| April | 13.1°C 56°F | 4.8°C 41°F | 9.0°C | 108 mm 4.2 in |
| May | 16.3°C 61°F | 7.6°C 46°F | 12.0°C | 108 mm 4.2 in |
| June | 18.7°C 66°F | 10.3°C 51°F | 14.6°C | 114 mm 4.5 in |
| July | 20.3°C 69°F | 12.1°C 54°F | 16.3°C | 128 mm 5.0 in |
| August | 19.9°C 68°F | 12.0°C 54°F | 16.0°C | 154 mm 6.1 in |
| September | 17.6°C 64°F | 9.9°C 50°F | 13.8°C | 147 mm 5.8 in |
| October | 14.0°C 57°F | 7.5°C 46°F | 10.8°C | 216 mm 8.5 in |
| November | 10.4°C 51°F | 4.5°C 40°F | 7.5°C | 208 mm 8.2 in |
| December | 8.1°C 47°F | 2.5°C 37°F | 5.3°C | 228 mm 9.0 in |
| Year | 13.7°C | 6.5°C | 10.1°C | 1,923 mm |
Where Ystradgynlais’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the 1 Met Office 2 km grid square whose centre lies inside Ystradgynlais’s built-up area.
- Highs and lows: the Met Office publishes average daily maxima and minima on its 12 km grid; each is moved by the difference between the town’s 2 km mean temperature and the 12 km square’s, which carries the town’s own height and setting over.
- Weather station and sunshine: Met Office historic station data for Cardiff Bute Park, 32 miles away, months of 1991–2020 averaged.
- Comparisons: every town and city of 2,500 or more across the UK, all four nations, read the same way.
Met Office HadUK-Grid · Met Office Climate Data Portal · Historic station data. Open Government Licence v3.0.
Questions about Ystradgynlais’s climate
How warm does Ystradgynlais get in summer?
July is the warmest month, with average highs of 20.3°C (69°F). About 8 days a year reach 25°C (77°F), fewer than 64% of UK towns.
How cold does Ystradgynlais get in winter?
February nights average 2.0°C (36°F). The air drops below freezing on about 38 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does Ystradgynlais get?
About 1,923 mm (76 in) a year, more than almost every UK town. December is the wettest month (228 mm) and April the driest (108 mm).
Where do these figures come from?
The Met Office’s HadUK-Grid 1991–2020 averages, which turn thousands of weather stations into a map of the UK in 2 km squares; the page reads the squares inside Ystradgynlais. They are 30-year averages, not a forecast.
Contains Met Office data © Crown copyright 2026, Open Government Licence v3.0. HadUK-Grid 1991–2020 averages via the Met Office Climate Data Portal; station averages from Met Office historic station data. Today’s forecast for Ystradgynlais →
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