Photo: Jaggery · CC BY-SA 2.0Ystrad Mynach is among the wettest of UK towns: 1,637 mm (64 in) of rain a year
Midwinter brings lows of about 2.0°C (36°F). Its July afternoons stay fresher than in 68% of UK towns. The rainiest month is December; the driest is May. Radiators earn their keep from November to April, the months that average under 10°C.
Met Office 1991–2020 averages for the town itself.
A year in Ystrad Mynach at a glance
Each month’s typical high and low, in °C.
What a year in Ystrad Mynach feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,637 mm of rain a year
December is the wettest month and May the driest. About 49 days a year bring 10 mm (0.4 in) or more. 5th wettest of 38 Gwent towns of 2,500+.
Rain by month
Millimetres
40 air frosts and 9 days of 25°C a year
On about 40 nights a year the air drops below freezing, and on about 1 days it stays below freezing all day. About 9 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 11 miles south of Ystrad Mynach, 9 m (30 ft) above sea level. It is the nearest of the 37 long-running stations the Met Office publishes in full.
| 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 Ystrad Mynach 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 Gwent 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 |
|---|---|---|---|
| Ystrad Mynach | 20.4°C | 2.0°C | 1,637 mm |
| Maesycwmmer 0.6 mi | 20.4°C about the same | 2.2°C about the same | 1,653 mm |
| Fleur-de-lis and Pengam 1.2 mi | 20.4°C about the same | 2.0°C about the same | 1,637 mm |
| Tir-y-berth and Glan-y-nant 1.2 mi | 20.4°C about the same | 1.9°C about the same | 1,525 mm |
| Pen-pedair-heol 1.3 mi | 20.4°C about the same | 1.9°C about the same | 1,525 mm |
| Gelligaer 1.4 mi | 20.5°C about the same | 1.8°C about the same | 1,720 mm |
| Blackwood 1.8 mi | 20.4°C about the same | 1.7°C about the same | 1,538 mm |
Ystrad Mynach 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 | 7.4°C 45°F | 2.0°C 36°F | 4.7°C | 145 mm 5.7 in |
| February | 7.5°C 46°F | 1.6°C 35°F | 4.5°C | 148 mm 5.8 in |
| March | 9.6°C 49°F | 2.5°C 37°F | 6.1°C | 122 mm 4.8 in |
| April | 12.9°C 55°F | 4.4°C 40°F | 8.6°C | 97 mm 3.8 in |
| May | 16.1°C 61°F | 7.2°C 45°F | 11.6°C | 97 mm 3.8 in |
| June | 18.8°C 66°F | 10.1°C 50°F | 14.4°C | 97 mm 3.8 in |
| July | 20.4°C 69°F | 11.8°C 53°F | 16.1°C | 104 mm 4.1 in |
| August | 20.0°C 68°F | 11.7°C 53°F | 15.9°C | 124 mm 4.9 in |
| September | 17.5°C 63°F | 9.5°C 49°F | 13.4°C | 126 mm 5.0 in |
| October | 13.6°C 56°F | 7.0°C 45°F | 10.3°C | 185 mm 7.3 in |
| November | 10.0°C 50°F | 4.2°C 39°F | 7.0°C | 184 mm 7.3 in |
| December | 7.6°C 46°F | 2.2°C 36°F | 4.8°C | 207 mm 8.1 in |
| Year | 13.4°C | 6.2°C | 9.8°C | 1,637 mm |
Where Ystrad Mynach’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the Met Office 2 km grid square nearest Ystrad Mynach’s centre (the town is smaller than one square).
- 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, 11 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 Ystrad Mynach’s climate
How warm does Ystrad Mynach get in summer?
July is the warmest month, with average highs of 20.4°C (69°F). About 9 days a year reach 25°C (77°F), fewer than 60% of UK towns.
How cold does Ystrad Mynach get in winter?
February nights average 1.6°C (35°F). The air drops below freezing on about 40 nights a year, and about 1 days a year stay below freezing all day.
How much rain does Ystrad Mynach get?
About 1,637 mm (64 in) a year, more than 98% of UK towns. December is the wettest month (207 mm) and May the driest (97 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 Ystrad Mynach. 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 Ystrad Mynach →
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