Compare the climate averages
These are 1991–2020 climate averages, not a forecast for your visit. The daily high and low columns average many days over that period; they are not limits on how hot or cold a particular day can become. Precipitation is the average monthly total.
| City | Monthly mean (°C) | Average daily high (°C) | Average daily low (°C) | Monthly precipitation (mm) | Relative humidity |
|---|---|---|---|---|---|
| Busan (부산) | 22.6 | 26.4 | 19.8 | 160.6 | 72.6% |
| Daegu (대구) | 22.1 | 27.0 | 18.0 | Not available in this dataset | Not available in this dataset |
| Gangneung (강릉) | 20.5 | 24.6 | 17.0 | 229.3 | 73.0% |
| Gyeongju (경주) | 20.5 | 26.2 | 16.2 | 194.1 | 81.3% |
| Incheon (인천) | 21.5 | 25.8 | 18.1 | 130.3 | 72.9% |
| Jeju (제주) | 23.3 | 26.1 | 20.9 | 227.8 | 73.7% |
| Seoul (서울) | 21.6 | 26.2 | 17.7 | 141.5 | 66.4% |
| Sokcho (속초) | 20.1 | 24.0 | 16.5 | 200.6 | 77.8% |
Source: Korea Meteorological Administration, 1991–2020 climate normals. A missing value means it is unavailable in the dataset used here, not that the city has no rain or that no other climate record exists. The selected table does not cover every Korean city.
Allow for a gradual change in the weather
September is cooler on average than August, but hot conditions may continue, especially early in the month. There is no fixed date when the heat ends.
Bring clothing for warm days and a layer for cooler evenings. Inland, coastal and mountain conditions can differ substantially within the same trip.
Rain also remains possible. The climate table shows 141.5 mm of average September precipitation in Seoul, 229.3 mm in Gangneung and 227.8 mm in Jeju. These are monthly totals, not predictions for your travel dates.
Keep typhoon disruption in mind
Typhoons can affect Korea in September, including rain, strong wind and rough seas away from the storm centre. Use current warnings and operator notices rather than converting a monthly storm average into a probability for your holiday.
Check ferries and flights before travelling to the terminal. Allow flexibility where an island journey connects with an essential departure, and follow local safety instructions if a storm approaches.
A rain jacket is useful for ordinary wet weather, but it does not make a closed trail, flooded path or rough sea safe.
Plan around Chuseok
Chuseok is the Korean autumn harvest holiday. The celebration itself falls on 25 September 2026 and 15 September 2027; the public-holiday periods are 24–26 September 2026 and 14–16 September 2027.
The official 2026 and 2027 calendar announcements identify the dates. Weekends next to the statutory break can extend the busy travel period.
Long-distance transport may be heavily booked, and some businesses close for family celebrations. Others remain open or run special programmes. Reserve essential journeys when sales open and confirm the restaurants and attractions important to your itinerary.
Do not assume that every museum is free or every neighbourhood closes. Holiday opening arrangements are announced by the individual operator.
Check beaches and events individually
Many beaches end their managed swimming season before September, while some operate later. Confirm lifeguard hours, the permitted swimming area and the day's conditions at the actual beach.
The end of swimming supervision does not necessarily close access for a walk, but warm weather does not extend permission to swim automatically.
For an event such as the Seoul International Fireworks Festival, consult the official organiser. Event dates can move between months, and a previous edition is not a standing annual schedule.
Choose autumn activities according to conditions
Parks, palaces and city walks may become more comfortable as temperatures ease. Mountain foliage can develop earlier than urban trees, but September is not a guarantee of widespread autumn colour.
Use local reports and the forecast when choosing an excursion. Keep rain protection, comfortable shoes and sun protection available, and adjust the day's pace if summer heat persists.
