Photo: Jaggery · CC BY-SA 2.0Ynysybwl is among the wettest of UK towns: 1,800 mm (71 in) of rain a year
The coldest hours of a January night bottom out at 1.9°C (35°F) on average. The gap between a January night and a July afternoon is 19°C. Summers stay cool: July afternoons here are cooler than in 69% of UK towns. Frost greets about 42 mornings a year, so leave time to clear the car.
Met Office 1991–2020 averages for the town itself.
A year in Ynysybwl at a glance
Each month’s typical high and low, in °C.
What a year in Ynysybwl feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,800 mm of rain a year
December is the wettest month and April the driest. About 62 days a year bring 10 mm (0.4 in) or more. 16th wettest of 32 Mid Glamorgan towns of 2,500+.
Rain by month
Millimetres
42 air frosts and 7 days of 25°C a year
On about 42 nights a year the air drops below freezing, and on about 1 days it stays below freezing all day. About 7 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 12 miles south-east of Ynysybwl, 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 Ynysybwl 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 Mid Glamorgan 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 |
|---|---|---|---|
| Ynysybwl | 20.3°C | 1.9°C | 1,800 mm |
| Abercynon 1.6 mi | 20.3°C about the same | 1.8°C about the same | 1,802 mm |
| Porth 2.6 mi | 19.9°C about the same | 1.7°C about the same | 2,153 mm |
| Wattstown 2.7 mi | 20.0°C about the same | 1.5°C about the same | 2,114 mm |
| Pontypridd 2.8 mi | 20.9°C 0.5°C warmer | 2.1°C about the same | 1,686 mm |
| Treharris 2.9 mi | 20.3°C about the same | 2.2°C about the same | 1,780 mm |
| Mountain Ash 3.2 mi | 19.8°C 0.5°C cooler | 1.7°C about the same | 2,024 mm |
Ynysybwl 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 | 7.3°C 45°F | 1.9°C 35°F | 4.6°C | 209 mm 8.2 in |
| February | 7.5°C 46°F | 1.8°C 35°F | 4.6°C | 161 mm 6.3 in |
| March | 9.6°C 49°F | 2.8°C 37°F | 6.2°C | 130 mm 5.1 in |
| April | 12.8°C 55°F | 4.5°C 40°F | 8.7°C | 101 mm 4.0 in |
| May | 16.0°C 61°F | 7.3°C 45°F | 11.7°C | 104 mm 4.1 in |
| June | 18.7°C 66°F | 10.3°C 50°F | 14.5°C | 105 mm 4.1 in |
| July | 20.3°C 69°F | 12.0°C 54°F | 16.2°C | 105 mm 4.1 in |
| August | 19.9°C 68°F | 11.9°C 53°F | 16.0°C | 127 mm 5.0 in |
| September | 17.4°C 63°F | 9.7°C 49°F | 13.5°C | 129 mm 5.1 in |
| October | 13.6°C 57°F | 7.1°C 45°F | 10.4°C | 195 mm 7.7 in |
| November | 10.0°C 50°F | 4.3°C 40°F | 7.1°C | 199 mm 7.8 in |
| December | 7.6°C 46°F | 2.3°C 36°F | 5.0°C | 235 mm 9.3 in |
| Year | 13.4°C | 6.3°C | 9.9°C | 1,800 mm |
Where Ynysybwl’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 Ynysybwl’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, 12 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 Ynysybwl’s climate
How warm does Ynysybwl get in summer?
July is the warmest month, with average highs of 20.3°C (69°F). About 7 days a year reach 25°C (77°F), fewer than 66% of UK towns.
How cold does Ynysybwl get in winter?
February nights average 1.8°C (35°F). The air drops below freezing on about 42 nights a year, and about 1 days a year stay below freezing all day.
How much rain does Ynysybwl get?
About 1,800 mm (71 in) a year, more than almost every UK town. December is the wettest month (235 mm) and April the driest (101 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 Ynysybwl. 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 Ynysybwl →
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