Month by month
| Month | Afternoon | Sea | Rain | Verdict |
|---|---|---|---|---|
| January | 7.5 °C | 8.8 °C | 14 days | Unfavourable season |
| February | 8.9 °C | 7.9 °C | 12 days | Unfavourable season |
| March | 10.6 °C | 8.1 °C | 14 days | Unfavourable season |
| April | 13 °C | 9.7 °C | 11 days | Possible, with trade-offs |
| May | 16.1 °C | 12.1 °C | 10 days | Possible, with trade-offs |
| June | 19.6 °C | 15.4 °C | 10 days | Pleasant — a good time to go |
| July | 21.6 °C | 17.8 °C | 11 days | Pleasant — a good time to go |
| August | 22 °C | 18.9 °C | 12 days | Pleasant — a good time to go |
| September | 19.7 °C | 18.3 °C | 11 days | Pleasant — a good time to go |
| October | 15.9 °C | 15.9 °C | 15 days | Possible, with trade-offs |
| November | 11.3 °C | 13.3 °C | 15 days | Unfavourable season |
| December | 9.1 °C | 10.5 °C | 15 days | Unfavourable season |
Before you go
Three things to check once you have picked your dates.
Entry
France is in the European Union. Entry rules depend on your nationality — check before booking.
Safety
No specific restrictions
Usual precautions apply.
Official advice updated 11 August 2026
Health
Recommended vaccinations, water quality, mosquitoes: advice depends on the country and the season. Some vaccines need time before departure.
Beau Fixe is not a safety or health authority. These notes summarise public advisories and link to their source; only the competent authorities are authoritative. Alert levels: Foreign, Commonwealth & Development Office (gov.uk), Open Government Licence v3.0.
FAQ
Can you swim in Grande-Synthe in October?
The sea averages 15.9°C in October — too cold for most swimmers.
How hot is Grande-Synthe in October?
Expect 15.9°C in the afternoon and 10.5°C at night, averaged over the last 10 years.
Does it rain a lot in Grande-Synthe in October?
Around 15 days with rain (≥ 1 mm) in the month — 47% of days.