Trethomas is among the wettest of UK towns: 1,444 mm (57 in) of rain a year
January nights here settle around 1.9°C (35°F). The rainiest month is December; the driest is June. About 44 nights a year bring a frost, more than in 63% of UK towns. The heating season runs November to April: each of those months averages under 10°C.
Met Office 1991–2020 averages for the town itself.
A year in Trethomas at a glance
Each month’s typical high and low, in °C.
What a year in Trethomas feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,444 mm of rain a year
December is the wettest month and June the driest. About 49 days a year bring 10 mm (0.4 in) or more.
Rain by month
Millimetres
44 air frosts and 12 days of 25°C a year
On about 44 nights a year the air drops below freezing, and on about under 1 days it stays below freezing all day. About 12 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 7.3 miles south of Trethomas, 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 Trethomas 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 |
|---|---|---|---|
| Trethomas | 21.0°C | 1.9°C | 1,444 mm |
| Bedwas 1.3 mi | 21.0°C about the same | 2.0°C about the same | 1,446 mm |
| Machen 1.3 mi | 20.8°C about the same | 1.2°C 0.7°C colder | 1,454 mm |
| Cwmfelinfach 1.7 mi | 20.8°C about the same | 1.4°C about the same | 1,450 mm |
| Llanbradach 2.8 mi | 21.1°C about the same | 1.7°C about the same | 1,537 mm |
| Caerphilly 2.9 mi | 21.0°C about the same | 1.9°C about the same | 1,448 mm |
| Risca 3.0 mi | 21.4°C about the same | 1.7°C about the same | 1,372 mm |
Trethomas 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 | 1.9°C 35°F | 4.7°C | 158 mm 6.2 in |
| February | 7.8°C 46°F | 1.5°C 35°F | 4.6°C | 117 mm 4.6 in |
| March | 10.2°C 50°F | 2.7°C 37°F | 6.5°C | 105 mm 4.1 in |
| April | 13.4°C 56°F | 4.4°C 40°F | 8.9°C | 86 mm 3.4 in |
| May | 16.6°C 62°F | 7.1°C 45°F | 11.8°C | 89 mm 3.5 in |
| June | 19.3°C 67°F | 10.0°C 50°F | 14.6°C | 86 mm 3.4 in |
| July | 21.0°C 70°F | 11.8°C 53°F | 16.4°C | 97 mm 3.8 in |
| August | 20.5°C 69°F | 11.7°C 53°F | 16.1°C | 117 mm 4.6 in |
| September | 18.1°C 65°F | 9.7°C 49°F | 13.8°C | 106 mm 4.2 in |
| October | 14.0°C 57°F | 7.1°C 45°F | 10.5°C | 154 mm 6.1 in |
| November | 10.3°C 51°F | 4.0°C 39°F | 7.1°C | 159 mm 6.3 in |
| December | 7.8°C 46°F | 2.0°C 36°F | 4.9°C | 171 mm 6.7 in |
| Year | 13.9°C | 6.1°C | 10.0°C | 1,444 mm |
Where Trethomas’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 Trethomas’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, 7.3 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 Trethomas’s climate
How warm does Trethomas get in summer?
July is the warmest month, with average highs of 21.0°C (70°F). About 12 days a year reach 25°C (77°F), more than 57% of UK towns.
How cold does Trethomas get in winter?
February nights average 1.5°C (35°F). The air drops below freezing on about 44 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does Trethomas get?
About 1,444 mm (57 in) a year, more than 95% of UK towns. December is the wettest month (171 mm) and June the driest (86 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 Trethomas. 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 Trethomas →
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.