What September feels like in Seoul
September is early autumn in Seoul. Warm daytime weather invites long lunches outside and evening strolls. Evenings bring a clear drop in temperature, and nights stay mild. Thick, humid air means clothes cling and the heat feels stronger than the number.
Rain in Seoul in September
It is a changeable month: rain comes about one day in 4, with dry spells in between. When rain comes it is heavy, about 16.9 mm (0.7 in) per wet day, often in short, strong bursts. That is heavier than Seoul's usual 12.8 mm per rainy day across the year. It is among the three wettest months of the year.
Daylight and sunshine in September
In mid-September, sunrise is at about 6:13 am and sunset at about 6:42 pm (local time) — 12 h 29 min of daylight. Compared with mid-August, the day has lost 1 h 10 min. The sun is out for roughly 67% of those daylight hours, so there are plenty of bright spells.
How September compares to the rest of the year
Ranked by average high, September comes out as the 4th warmest month in Seoul. Against August, the average high is 4°C (7.2°F) lower, with 122 mm less rain. The cooling trend carries on into October. October averages a high of 19°C (66.2°F).
Who September suits
- Sightseeing: a good fit — the weather rarely gets in the way of a city walk.
- Parks & outdoor: a good fit — good conditions for sitting outside.
Tips for visiting Seoul in September
Versatile Layers
Days are noticeably warmer than nights — layers you can add or remove.
Rain Protection
Keep a small umbrella in your bag and wear shoes that cope with puddles.
Sunglasses
Frequent sunshine — sunglasses and a light hat.
Quick questions
How warm is Seoul in September?
It feels warm: typical highs are 25.1°C (77.2°F), with lows near 17°C (62.6°F).
Does it rain a lot in Seoul in September?
It does: about 8 rainy days bring roughly 135 mm, so plan some indoor options.
What should I wear in Seoul in September?
Based on the averages: versatile layers, rain protection and sunglasses. Add a layer for after dark.
Is September or October better for visiting Seoul?
On our 12-month climate ranking, October comes out ahead (#1 of 12 vs #3). October is cooler and has fewer rainy days.