South Korea in September: Weather, Crowds & What to Expect
Climate Map for September
Average temperature across South Korea in September.
City Weather in September
| City | High | Low | Rain | UV | Feels |
|---|---|---|---|---|---|
| Seoul | 25° | 16° | 150 mm | high | Mild |
| Busan | 26° | 18° | 172 mm | high | Mild |
| Incheon | 25° | 16° | 148 mm | high | Mild |
| Daegu | 26° | 16° | 134 mm | high | Mild |
| Daejeon | 26° | 15° | 148 mm | high | Mild |
| Gwangju | 27° | 17° | 142 mm | high | Mild |
| Suwon | 25° | 15° | 151 mm | high | Mild |
High / low are average daily temperatures (°C). “Feels” reflects how hot or cold it feels, allowing for humidity.
Seoul & Northwest (Gyeonggi, Incheon, Yellow Sea coast)
September feels like a reset: cooler mornings and a dramatic drop in humidity reward outdoor plans, and the city skyline is crisply visible. Autumn foliage begins to tint the mountains around Seoul by late September, and major festivals resume with comfortable temperatures ideal for walking tours. Pack a light jacket for evenings and expect busier tourist sites as both locals and overseas visitors take advantage of the clear weather.
Gangwon Province & the Taebaek Mountains (Sokcho, Pyeongchang, Seoraksan)
September brings relief from humidity and a return of clear, cool air that makes mountain trekking exceptional; fall colors begin late in the month on the higher ridges. Gangneung’s coffee street and Sokcho’s fish markets are pleasant, and the friendlier weather is great for Jeongseon rail-bike rides. Expect weekends to be busier with day-trippers from Seoul taking advantage of the crisp weather.
Central Korea (Chungcheong, Daejeon, Cheongju, Boryeong)
September brings dramatic improvement: humidity falls and the air clears, producing ideal conditions for sightseeing and outdoor activities. Late-summer rice harvests give the countryside a golden look, and temple stays are pleasant with cool nights. Daylight remains long enough for leisurely exploration; bring a light jacket for evenings and expect busier weekends as Koreans travel for the fine weather.
Yeongnam / Southeast (Busan, Daegu, Ulsan, Gyeongsang)
September cools quickly into clear, comfortable weather that highlights coastal scenery and makes city walking pleasurable; Gyeongju’s historic sites are especially nice with fewer bugs and pleasant daylight. This is an excellent time for seafood and coastal drives, though occasional typhoon remnants can still arrive early in the month. Bring a light jacket for evenings and expect increased weekend travel by domestic tourists.
Jeolla & Southwest (Gwangju, Mokpo, Suncheon, Boseong)
September brings welcome relief as typhoon risk tails off and humidity drops, leaving warm days and cool nights perfect for cycling around the rural countryside and exploring Suncheon Bay. Autumn color starts late in the month in higher ground, and seafood is at its best with calmer seas. Expect increased domestic weekend travel but generally excellent conditions for outdoor activities.
Jeju Island (Hallasan, Seogwipo, Jeju City, Udo)
September often brings relief from heat and humidity, with many clear, calm days perfect for hiking Hallasan and walking the Olle routes. Typhoon chance drops through the month but remnants are possible early on - coastal waters remain warm and good for snorkeling on clearer days. Bring a light sweater for evenings and expect the island to be lively as locals return after summer holidays.