Île-de-Sein has some of the coolest summers among mainland French towns
The depth of winter brings overnight lows near 5.2°C. Expect the heaviest rain in November and the lightest in June. Its January nights stay gentler than in 98% of mainland French towns. Picnics, hikes and garden evenings come into their own from June to September, with highs of 19–21°C.
Figures from Météo-France’s Lanvéoc station, 41 km north-east: at that distance, read them as the area’s climate rather than the town’s.
A year in Île-de-Sein at a glance
Each month’s typical high and low in °C, at the Lanvéoc station.
What a year in Île-de-Sein feels like
Typical highs and lows by season and by month, from Météo-France’s 1991–2020 normals at Lanvéoc.
About 1,030 mm of rain a year
November is the wettest month and June the driest. About 32 days a year bring 10 mm or more. 68th wettest of 91 towns of 2,500+ in Finistère.
Rain by month
Millimeters
Sunshine by month
Hours of sunshine at Lanvéoc
9 frosts and 12 days of 25°C a year
On about 9 nights a year the air drops to 0°C or below; days that stay below freezing are rare. About 12 days a year reach 25°C, and under 1 reach 30°C.
Day counts are Météo-France’s 1991–2020 normals at Lanvéoc: a frost is a night of 0°C or below, a summer day (jour d’été) 25°C or more, a hot day (forte chaleur) 30°C or more.
The Météo-France station at Lanvéoc
Lanvéoc is 41 km north-east of Île-de-Sein. Every figure on this page is the station’s, not a measurement in Île-de-Sein itself. At that distance, read them as the area’s climate.
| Station (Météo-France number) | Lanvéoc (29120001) |
| Distance from the town | 41 km north-east |
| Station altitude | 81 m |
| Town altitude (its center) | 5 m |
| Period | 1991–2020 |
| Sunshine measured at | the same station |
TownRatings matches each commune to one station with at least 24 years of temperature and rain records: the nearest, counting every 100 m of height difference as 10 km, never across the sea.
How Île-de-Sein compares
Against the 4,385 towns of 2,500 or more in mainland France, each read from its own matched station. The dots are the other towns of 2,500+ in Finistère.
Nearby towns’ climate
The nearest towns of 2,500+ within 29 km. Where a neighbor uses the same station its figures are the same: the differences you’d feel over a few kilometers aren’t in the normals.
Île-de-Sein weather by month
Average daily high and low, mean temperature and rain, 1991–2020, at the Lanvéoc station.
| Month | High | Low | Mean | Rain | Sun (hours) |
|---|---|---|---|---|---|
| January | 9.8°C | 5.2°C | 7.5°C | 118 mm | 61 |
| February | 10.1°C | 4.8°C | 7.5°C | 98 mm | 81 |
| March | 12.0°C | 5.9°C | 9.0°C | 72 mm | 124 |
| April | 14.1°C | 7.1°C | 10.6°C | 75 mm | 164 |
| May | 16.8°C | 9.7°C | 13.2°C | 61 mm | 192 |
| June | 19.2°C | 12.1°C | 15.7°C | 56 mm | 208 |
| July | 20.9°C | 13.8°C | 17.4°C | 57 mm | 194 |
| August | 21.0°C | 14.0°C | 17.5°C | 62 mm | 190 |
| September | 19.5°C | 12.5°C | 16.0°C | 70 mm | 175 |
| October | 16.1°C | 10.5°C | 13.3°C | 108 mm | 112 |
| November | 12.7°C | 7.9°C | 10.3°C | 127 mm | 71 |
| December | 10.5°C | 5.9°C | 8.2°C | 127 mm | 65 |
| Year | 15.2°C | 9.1°C | 12.2°C | 1,030 mm | 1,636 |
Where Île-de-Sein’s numbers come from
Averages over 30 years, not a forecast.
- Temperature, rain and day counts: Météo-France’s fiche climatologique for Lanvéoc, 41 km away: statistics for 1991–2020.
- Which station: among stations with at least 24 of the 30 years of temperature and rain, the nearest to the commune’s population-weighted center, counting each 100 m of height difference as 10 km; mainland towns use mainland stations and each overseas département its own.
- Altitudes: the town’s from IGN’s RGE ALTI® at its population-weighted center; the station’s from Météo-France.
- Sunshine: the nearest station with at least 10 years of sunshine records, Lanvéoc, 41 km away.
- Comparisons: every town of 2,500 or more in mainland France, read the same way; the dots are the towns of 2,500+ in Finistère.
Météo-France fiches climatologiques · IGN RGE ALTI®. Licence Ouverte 2.0.
Questions about Île-de-Sein’s climate
How warm does Île-de-Sein get in summer?
August is the warmest month, with average highs of 21.0°C. About 12 days a year reach 25°C, fewer than 98% of mainland French towns, and about under 1 reach 30°C.
How cold does Île-de-Sein get in winter?
February nights average 4.8°C. The air drops to 0°C or below on about 9 nights a year, and about under 1 days a year stay below freezing all day.
How much rain does Île-de-Sein get?
About 1,030 mm a year, more than 88% of mainland French towns. November is the wettest month (127 mm) and June the driest (56 mm).
How sunny is it?
The nearest Météo-France station that records sunshine, Lanvéoc (41 km away), averages 1,636 hours of sunshine a year.
Are these figures for Île-de-Sein itself?
No: they are the normals of the Météo-France station matched to Île-de-Sein, Lanvéoc, 41 km away. France publishes its climate normals by station, not by commune; a valley, a hill or the sea can make a difference over a few kilometers.
Where do these figures come from?
Météo-France’s fiches climatologiques: 30-year averages (1991–2020) for each of its long-running stations, published as open data since 2024. They are normals, not a forecast.
Source: Météo-France, fiches climatologiques, 1991–2020 statistics (station LANVEOC, edited 15/10/2026); altitude: IGN, RGE ALTI®. Licence Ouverte 2.0. Today’s forecast for Île-de-Sein →
Contains public sector information under the Licence Ouverte / Open Licence 2.0 (Etalab): INSEE, DGFiP, the Interior Ministry’s statistics service (SSMSI), the Ministry of Education (DEPP), the Health Ministry’s statistics service (DREES) and the Housing Ministry (Carte des loyers). Commune boundaries: IGN Admin Express.