Blackmill sits near the top of UK towns for rain, with 1,621 mm (64 in) a year
Midsummer highs settle at about 20.4°C (69°F). Days of 25°C are scarce: about 6 a year, fewer than in 72% of UK towns. Wet weather is most frequent in January and least in April. Keep the boiler serviced for the months from November to April, which average under 10°C.
Met Office 1991–2020 averages for the town itself.
A year in Blackmill at a glance
Each month’s typical high and low, in °C.
What a year in Blackmill feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,621 mm of rain a year
January is the wettest month and April the driest. About 66 days a year bring 10 mm (0.4 in) or more.
Rain by month
Millimetres
44 air frosts and 6 days of 25°C a year
On about 44 nights a year the air drops below freezing, and on about 1 days it stays below freezing all day. About 6 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 16 miles east of Blackmill, 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 Blackmill 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 |
|---|---|---|---|
| Blackmill | 20.4°C | 1.6°C | 1,621 mm |
| Llangeinor 1.4 mi | 19.9°C 0.6°C cooler | 1.6°C about the same | 2,045 mm |
| Bettws 2.2 mi | 19.9°C 0.6°C cooler | 2.0°C about the same | 2,029 mm |
| Ogmore Vale 2.3 mi | 19.9°C 0.6°C cooler | 1.4°C about the same | 2,068 mm |
| Sarn 2.7 mi | 20.6°C about the same | 2.3°C 0.6°C milder | 1,487 mm |
| Gilfach Goch 3.1 mi | 20.1°C about the same | 0.8°C 0.8°C colder | 2,103 mm |
| Hendreforgan 3.1 mi | 20.3°C about the same | 1.5°C about the same | 1,868 mm |
Blackmill 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 | 1.6°C 35°F | 4.5°C | 195 mm 7.7 in |
| February | 8.1°C 47°F | 2.1°C 36°F | 5.1°C | 125 mm 4.9 in |
| March | 10.3°C 51°F | 3.2°C 38°F | 6.8°C | 113 mm 4.4 in |
| April | 13.2°C 56°F | 4.8°C 41°F | 9.0°C | 91 mm 3.6 in |
| May | 16.4°C 61°F | 7.4°C 45°F | 11.9°C | 92 mm 3.6 in |
| June | 18.8°C 66°F | 10.2°C 50°F | 14.5°C | 94 mm 3.7 in |
| July | 20.4°C 69°F | 12.2°C 54°F | 16.3°C | 118 mm 4.6 in |
| August | 20.2°C 68°F | 11.9°C 53°F | 16.2°C | 134 mm 5.3 in |
| September | 18.1°C 65°F | 10.0°C 50°F | 14.0°C | 122 mm 4.8 in |
| October | 14.5°C 58°F | 7.4°C 45°F | 11.0°C | 175 mm 6.9 in |
| November | 10.9°C 52°F | 4.8°C 41°F | 7.8°C | 178 mm 7.0 in |
| December | 8.4°C 47°F | 2.6°C 37°F | 5.5°C | 185 mm 7.3 in |
| Year | 13.9°C | 6.5°C | 10.2°C | 1,621 mm |
Where Blackmill’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 Blackmill’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, 16 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 Blackmill’s climate
How warm does Blackmill get in summer?
July is the warmest month, with average highs of 20.4°C (69°F). About 6 days a year reach 25°C (77°F), fewer than 72% of UK towns.
How cold does Blackmill get in winter?
January nights average 1.6°C (35°F). The air drops below freezing on about 44 nights a year, and about 1 days a year stay below freezing all day.
How much rain does Blackmill get?
About 1,621 mm (64 in) a year, more than 98% of UK towns. January is the wettest month (195 mm) and April the driest (91 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 Blackmill. 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 Blackmill →
Contains public sector information licensed under the Open Government Licence v3.0. Contains HM Land Registry data © Crown copyright and database right 2026. Contains OS data © Crown copyright and database right 2026 (ONS boundaries). Northern Ireland: Source: NISRA; contains Land & Property Services data and Ordnance Survey of Northern Ireland information, © Crown copyright, licensed under the Open Government Licence v3.0. Scotland: contains National Records of Scotland data, Registers of Scotland data and SEPA data, © Crown copyright / © SEPA 2025, licensed under the Open Government Licence v3.0.