Trelewis sits near the top of UK towns for rain, with 1,734 mm (68 in) a year
January nights here settle around 1.7°C (35°F). By July afternoons alone, it runs cooler than 72% of UK towns. Temperatures cover 19°C across the year, low to high. Expect about 44 frosty starts a year, nights when the air falls below freezing.
Met Office 1991–2020 averages for the town itself.
A year in Trelewis at a glance
Each month’s typical high and low, in °C.
What a year in Trelewis feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,734 mm of rain a year
December is the wettest month and April the driest. About 59 days a year bring 10 mm (0.4 in) or more.
Rain by month
Millimetres
44 air frosts and 7 days of 25°C a year
On about 44 nights a year the air drops below freezing, and on about 2 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 13 miles south of Trelewis, 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 Trelewis 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 |
|---|---|---|---|
| Trelewis | 20.2°C | 1.7°C | 1,734 mm |
| Treharris 0.6 mi | 20.3°C about the same | 2.2°C about the same | 1,780 mm |
| Nelson 1.2 mi | 20.2°C about the same | 2.0°C about the same | 1,725 mm |
| Gelligaer 1.7 mi | 20.5°C about the same | 1.8°C about the same | 1,720 mm |
| Abercynon 2.0 mi | 20.3°C about the same | 1.8°C about the same | 1,802 mm |
| Pen-pedair-heol 2.3 mi | 20.4°C about the same | 1.9°C about the same | 1,525 mm |
| Bedlinog 2.6 mi | 19.4°C 0.8°C cooler | 1.0°C 0.7°C colder | 1,750 mm |
Trelewis 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 | 7.1°C 45°F | 1.7°C 35°F | 4.4°C | 199 mm 7.8 in |
| February | 7.4°C 45°F | 1.7°C 35°F | 4.6°C | 154 mm 6.1 in |
| March | 9.5°C 49°F | 2.7°C 37°F | 6.1°C | 124 mm 4.9 in |
| April | 12.8°C 55°F | 4.5°C 40°F | 8.7°C | 98 mm 3.9 in |
| May | 16.0°C 61°F | 7.3°C 45°F | 11.7°C | 103 mm 4.0 in |
| June | 18.7°C 66°F | 10.3°C 50°F | 14.5°C | 100 mm 3.9 in |
| July | 20.2°C 68°F | 11.9°C 53°F | 16.1°C | 102 mm 4.0 in |
| August | 19.8°C 68°F | 11.8°C 53°F | 15.9°C | 121 mm 4.8 in |
| September | 17.3°C 63°F | 9.6°C 49°F | 13.5°C | 124 mm 4.9 in |
| October | 13.6°C 56°F | 7.1°C 45°F | 10.4°C | 189 mm 7.4 in |
| November | 9.9°C 50°F | 4.3°C 40°F | 7.1°C | 194 mm 7.6 in |
| December | 7.6°C 46°F | 2.3°C 36°F | 4.9°C | 227 mm 8.9 in |
| Year | 13.3°C | 6.2°C | 9.8°C | 1,734 mm |
Where Trelewis’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 Trelewis’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, 13 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 Trelewis’s climate
How warm does Trelewis get in summer?
July is the warmest month, with average highs of 20.2°C (68°F). About 7 days a year reach 25°C (77°F), fewer than 69% of UK towns.
How cold does Trelewis get in winter?
February nights average 1.7°C (35°F). The air drops below freezing on about 44 nights a year, and about 2 days a year stay below freezing all day.
How much rain does Trelewis get?
About 1,734 mm (68 in) a year, more than almost every UK town. December is the wettest month (227 mm) and April the driest (98 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 Trelewis. 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 Trelewis →
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.