Trawsfynydd sits near the top of UK towns for rain, with 2,029 mm (80 in) a year
Winter’s chill peaks in January, at about 2.0°C (36°F) after dark. In July, afternoons here are cooler than in 94% of UK towns. The year changes little: the coldest month’s nights and the warmest month’s afternoons are only 17°C apart. Gritters and ice scrapers earn their keep on roughly 41 nights a year below 0°C.
Met Office 1991–2020 averages for the town itself.
A year in Trawsfynydd at a glance
Each month’s typical high and low, in °C.
What a year in Trawsfynydd feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 2,029 mm of rain a year
December is the wettest month and April the driest. About 70 days a year bring 10 mm (0.4 in) or more.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Valley (Anglesey)
41 air frosts and 4 days of 25°C a year
On about 41 nights a year the air drops below freezing, and on about under 1 days it stays below freezing all day. About 4 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 Valley (Anglesey)
Valley (Anglesey) is 35 miles north-west of Trawsfynydd, 10 m (33 ft) above sea level. It is the nearest of the 37 long-running stations the Met Office publishes in full; at that distance read it for sunshine and the station’s own record, not as the town’s figures.
| Month | High | Low | Rain | Air frosts | Sun (hours) |
|---|---|---|---|---|---|
| January | 8.4°C | 3.8°C | 75 mm | 5.2 | 58 |
| February | 8.4°C | 3.6°C | 62 mm | 4.8 | 81 |
| March | 9.8°C | 4.5°C | 57 mm | 2.4 | 126 |
| April | 12.1°C | 6.1°C | 54 mm | 0.5 | 173 |
| May | 15.0°C | 8.6°C | 52 mm | 0.0 | 219 |
| June | 17.2°C | 11.0°C | 57 mm | 0.0 | 203 |
| July | 18.8°C | 12.9°C | 58 mm | 0.0 | 190 |
| August | 18.8°C | 13.1°C | 69 mm | 0.0 | 176 |
| September | 17.3°C | 11.6°C | 74 mm | 0.0 | 143 |
| October | 14.3°C | 9.2°C | 102 mm | 0.1 | 101 |
| November | 11.3°C | 6.6°C | 104 mm | 0.7 | 59 |
| December | 9.1°C | 4.4°C | 94 mm | 4.2 | 46 |
| Year | 13.4°C | 8.0°C | 857 mm | 18 | 1,575 |
Met Office historic station data, Valley, 1991–2020 months averaged (a month needs 20 of the 30 years; estimated values counted, missing months left out). Sunshine: Kipp & Zonen recorder.
How Trawsfynydd 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 Gwynedd 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 |
|---|---|---|---|
| Trawsfynydd | 18.8°C | 2.0°C | 2,029 mm |
| Blaenau Ffestiniog 6.4 mi | 18.1°C 0.7°C cooler | 1.4°C 0.7°C colder | 2,332 mm |
| Penrhyndeudraeth 6.5 mi | 19.5°C 0.6°C warmer | 3.1°C 1.1°C milder | 1,691 mm |
| Harlech 8.2 mi | 19.5°C 0.6°C warmer | 3.2°C 1.2°C milder | 1,364 mm |
| Porthmadog 9.0 mi | 19.8°C 0.9°C warmer | 3.0°C 1.0°C milder | 1,329 mm |
| Dolgellau 11.0 mi | 19.7°C 0.9°C warmer | 2.6°C 0.6°C milder | 1,755 mm |
Trawsfynydd 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 | 6.9°C 44°F | 2.0°C 36°F | 4.5°C | 207 mm 8.1 in |
| February | 7.3°C 45°F | 2.0°C 36°F | 4.7°C | 169 mm 6.7 in |
| March | 9.1°C 48°F | 2.9°C 37°F | 6.0°C | 147 mm 5.8 in |
| April | 12.1°C 54°F | 4.6°C 40°F | 8.3°C | 111 mm 4.4 in |
| May | 15.1°C 59°F | 7.1°C 45°F | 11.0°C | 113 mm 4.5 in |
| June | 17.4°C 63°F | 9.7°C 50°F | 13.5°C | 131 mm 5.1 in |
| July | 18.8°C 66°F | 11.6°C 53°F | 15.1°C | 137 mm 5.4 in |
| August | 18.5°C 65°F | 11.6°C 53°F | 15.1°C | 156 mm 6.2 in |
| September | 16.5°C 62°F | 9.8°C 50°F | 13.1°C | 166 mm 6.5 in |
| October | 13.2°C 56°F | 7.4°C 45°F | 10.2°C | 220 mm 8.6 in |
| November | 9.8°C 50°F | 4.6°C 40°F | 7.2°C | 226 mm 8.9 in |
| December | 7.7°C 46°F | 2.5°C 37°F | 5.1°C | 246 mm 9.7 in |
| Year | 12.7°C | 6.3°C | 9.5°C | 2,029 mm |
Where Trawsfynydd’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 Trawsfynydd’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 Valley, 35 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 Trawsfynydd’s climate
How warm does Trawsfynydd get in summer?
July is the warmest month, with average highs of 18.8°C (66°F). About 4 days a year reach 25°C (77°F), fewer than 82% of UK towns.
How cold does Trawsfynydd get in winter?
January nights average 2.0°C (36°F). The air drops below freezing on about 41 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does Trawsfynydd get?
About 2,029 mm (80 in) a year, more than almost every UK town. December is the wettest month (246 mm) and April the driest (111 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Valley (Anglesey) (35 miles away), averages 1,575 hours of bright sunshine a year. Sunshine isn’t on the town grid, so this is the station’s figure.
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 Trawsfynydd. 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 Trawsfynydd →
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.