Hardly any UK towns see softer January nights than Caernarfon
The warmest part of a July day comes in at 19.6°C (67°F) on average. The year changes little: the coldest month’s nights and the warmest month’s afternoons are only 16°C apart. By rainfall alone, it ranks wetter than 95% of UK towns. Plan time outside from June to September, when highs sit at 18–20°C.
Met Office 1991–2020 averages for the town itself.
A year in Caernarfon at a glance
Each month’s typical high and low, in °C.
What a year in Caernarfon feels like
Typical highs and lows by season and by month, from the Met Office’s 1991–2020 averages.
About 1,426 mm of rain a year
November is the wettest month and May the driest. About 42 days a year bring 10 mm (0.4 in) or more. 4th wettest of 13 Gwynedd towns of 2,500+.
Rain by month
Millimetres
Sunshine by month
Hours of bright sunshine at Valley (Anglesey)
18 air frosts and 5 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 5 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 14 miles north-west of Caernarfon, 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 Caernarfon 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 |
|---|---|---|---|
| Caernarfon | 19.6°C | 3.4°C | 1,426 mm |
| Bethel 3.1 mi | 19.3°C about the same | 3.1°C about the same | 1,569 mm |
| Llanrug 3.2 mi | 19.3°C about the same | 3.1°C about the same | 1,597 mm |
| Y Felinheli 3.8 mi | 20.0°C about the same | 3.4°C about the same | 1,076 mm |
| Clwt-y-bont 5.6 mi | 18.9°C 0.7°C cooler | 2.7°C 0.7°C colder | 2,028 mm |
| Gaerwen 5.7 mi | 19.7°C about the same | 3.0°C about the same | 1,142 mm |
| Llanberis 5.8 mi | 17.6°C 2.0°C cooler | 2.6°C 0.8°C colder | 2,530 mm |
Caernarfon 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 | 8.6°C 48°F | 3.4°C 38°F | 6.0°C | 123 mm 4.8 in |
| February | 8.7°C 48°F | 3.2°C 38°F | 5.9°C | 107 mm 4.2 in |
| March | 10.5°C 51°F | 4.1°C 39°F | 7.3°C | 98 mm 3.9 in |
| April | 12.9°C 55°F | 5.7°C 42°F | 9.2°C | 87 mm 3.4 in |
| May | 15.9°C 61°F | 8.3°C 47°F | 12.0°C | 78 mm 3.1 in |
| June | 18.1°C 65°F | 10.8°C 51°F | 14.4°C | 90 mm 3.5 in |
| July | 19.6°C 67°F | 12.5°C 55°F | 16.0°C | 112 mm 4.4 in |
| August | 19.5°C 67°F | 12.6°C 55°F | 16.0°C | 110 mm 4.3 in |
| September | 17.6°C 64°F | 10.9°C 52°F | 14.2°C | 121 mm 4.8 in |
| October | 14.5°C 58°F | 8.4°C 47°F | 11.4°C | 155 mm 6.1 in |
| November | 11.2°C 52°F | 5.8°C 42°F | 8.5°C | 182 mm 7.2 in |
| December | 9.0°C 48°F | 3.8°C 39°F | 6.4°C | 165 mm 6.5 in |
| Year | 13.8°C | 7.5°C | 10.6°C | 1,426 mm |
Where Caernarfon’s numbers come from
Averages over 30 years, not a forecast.
- Mean temperature, rain and day counts: HadUK-Grid 1991–2020 averages for the 1 Met Office 2 km grid square whose centre lies inside Caernarfon’s built-up area.
- 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, 14 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 Caernarfon’s climate
How warm does Caernarfon get in summer?
July is the warmest month, with average highs of 19.6°C (67°F). About 5 days a year reach 25°C (77°F), fewer than 78% of UK towns.
How cold does Caernarfon 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 Caernarfon get?
About 1,426 mm (56 in) a year, more than 95% of UK towns. November is the wettest month (182 mm) and May the driest (78 mm).
How sunny is it?
The nearest Met Office station with a sunshine record, Valley (Anglesey) (14 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 Caernarfon. 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 Caernarfon →
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.