Month by month
| Month | Afternoon | Sea | Rain | Verdict |
|---|---|---|---|---|
| January | 3.1 °C | 7.2 °C | 5 days | Unfavourable season |
| February | 5.1 °C | 5 °C | 5 days | Unfavourable season |
| March | 11 °C | 5.6 °C | 5 days | Unfavourable season |
| April | 16.9 °C | 8.7 °C | 7 days | Possible, with trade-offs |
| May | 21.7 °C | 13.1 °C | 7 days | Pleasant — a good time to go |
| June | 26.1 °C | 18.2 °C | 9 days | Ideal — one of the best times of year |
| July | 28.4 °C | 22.4 °C | 16 days | Possible, with trade-offs |
| August | 29.3 °C | 25.5 °C | 15 days | Possible, with trade-offs |
| September | 25.5 °C | 23.2 °C | 9 days | Ideal — one of the best times of year |
| October | 19 °C | 19.5 °C | 6 days | Possible, with trade-offs |
| November | 12.4 °C | 15.6 °C | 8 days | Possible, with trade-offs |
| December | 5 °C | 11.2 °C | 7 days | Unfavourable season |
Nearby in May
Before you go
Three things to check once you have picked your dates.
Entry
No visa needed for stays of up to 90 days. Passport valid until your return date. K-ETA not required for British nationals until 31 December 2026; onward or return ticket required; e-Arrival card can be submitted online within 72 hours.
For a British passport, per the UK Foreign Office on 14 May 2026. Rules change: check before booking.
Safety
No specific restrictions
Usual precautions apply.
Official advice updated 14 May 2026
Health
Vaccines · hepatitis A and hepatitis B if you are not already vaccinated; Japanese encephalitis depending on activities and areas visited. Routine vaccines up to date (measles in particular).
Yellow fever · No yellow fever locally, vaccine not recommended. No entry requirement.
Malaria · Present. Areas: Limited to the months of March–December in rural areas in the northern parts of the provinces of Incheon (also spelled Inch’ŏn), Gangwon (also spelled Kangwŏn), and Gyeonggi (also spelled Kyŏnggi), including the demilitarized zone (DMZ). Preventive medication recommended: Atovaquone-proguanil, chloroquine, doxycycline, mefloquine, primaquine , or tafenoquine — prescribed before departure.
Per the CDC (page reviewed 25 August 2026); see a travel clinic a few weeks before departure.
Beau Fixe is not a safety or health authority. These notes summarise dated public texts and link to their source: France Diplomatie (Licence Ouverte 2.0), Foreign, Commonwealth & Development Office (gov.uk, Open Government Licence v3.0), Centers for Disease Control and Prevention (Source: CDC). Only the competent authorities are authoritative.
FAQ
Can you swim in Seosan in May?
The sea averages 13.1°C in May — too cold for most swimmers.
How hot is Seosan in May?
Expect 21.7°C in the afternoon and 11.9°C at night, averaged over the last 10 years.
Does it rain a lot in Seosan in May?
Around 7 days with rain (≥ 1 mm) in the month — 23% of days.