Hardly any UK towns wake to less frost than Rhostryfan
In July the day’s top temperature is typically 18.9°C (66°F). A year here swings 16°C from midwinter lows to midsummer highs. Rain is plentiful here, more than falls on 96% of UK towns. Radiators earn their keep from November to April, the months that average under 10°C.
Met Office 1991–2020 averages for the town itself.
A year in Rhostryfan at a glance
Each month’s typical high and low, in °C.
What a year in Rhostryfan feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,475 mm of rain a year
November is the wettest month and May the driest. About 50 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)
18 air frosts and 4 days of 25°C a year
On about 18 nights a year the air drops below freezing; days that stay below freezing are rare. 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 16 miles north-west of Rhostryfan, 10 m (33 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 | 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 Rhostryfan 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 |
|---|---|---|---|
| Rhostryfan | 18.9°C | 3.4°C | 1,475 mm |
| Caernarfon 3.1 mi | 19.6°C 0.7°C warmer | 3.4°C about the same | 1,426 mm |
| Penygroes 3.3 mi | 18.7°C about the same | 3.4°C about the same | 1,684 mm |
| Llanrug 4.3 mi | 19.3°C about the same | 3.1°C about the same | 1,597 mm |
| Bethel 5.1 mi | 19.3°C about the same | 3.1°C about the same | 1,569 mm |
| Llanberis 5.2 mi | 17.6°C 1.3°C cooler | 2.6°C 0.7°C colder | 2,530 mm |
| Clwt-y-bont 6.0 mi | 18.9°C about the same | 2.7°C 0.6°C colder | 2,028 mm |
Rhostryfan 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 | 7.9°C 46°F | 3.4°C 38°F | 5.7°C | 144 mm 5.7 in |
| February | 8.2°C 47°F | 3.2°C 38°F | 5.7°C | 110 mm 4.3 in |
| March | 9.7°C 50°F | 4.1°C 39°F | 6.9°C | 101 mm 4.0 in |
| April | 12.3°C 54°F | 5.8°C 42°F | 8.9°C | 86 mm 3.4 in |
| May | 15.2°C 59°F | 8.4°C 47°F | 11.7°C | 78 mm 3.1 in |
| June | 17.4°C 63°F | 10.8°C 51°F | 14.0°C | 88 mm 3.5 in |
| July | 18.9°C 66°F | 12.7°C 55°F | 15.6°C | 107 mm 4.2 in |
| August | 18.7°C 66°F | 12.7°C 55°F | 15.7°C | 115 mm 4.5 in |
| September | 16.9°C 62°F | 11.1°C 52°F | 14.0°C | 126 mm 5.0 in |
| October | 14.0°C 57°F | 8.7°C 48°F | 11.3°C | 165 mm 6.5 in |
| November | 10.8°C 51°F | 6.0°C 43°F | 8.4°C | 186 mm 7.3 in |
| December | 8.6°C 47°F | 3.9°C 39°F | 6.4°C | 170 mm 6.7 in |
| Year | 13.2°C | 7.6°C | 10.4°C | 1,475 mm |
Where Rhostryfan’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 Rhostryfan’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, 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 Rhostryfan’s climate
How warm does Rhostryfan get in summer?
July is the warmest month, with average highs of 18.9°C (66°F). About 4 days a year reach 25°C (77°F), fewer than 83% of UK towns.
How cold does Rhostryfan get in winter?
February nights average 3.2°C (38°F). The air drops below freezing on about 18 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does Rhostryfan get?
About 1,475 mm (58 in) a year, more than 96% of UK towns. November is the wettest month (186 mm) and May the driest (78 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Valley (Anglesey) (16 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 Rhostryfan. 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 Rhostryfan →
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.