Seoul Weather in September
South Korea · Humid Continental climate · Data averaged from 2020-01-01 to 2024-12-31 (5 years)
September in Seoul sees average temperatures ranging from a low of 17.7°C (63.9°F) to a high of 25.5°C (77.9°F), with a mean of 21.3°C (70.3°F). Compared to the annual average of 11.9°C (53.4°F), this month is 9.4°C warmer than the yearly norm. Precipitation averages 198.6mm, making it approximately 72.0mm wetter than the monthly average of 126.0mm. The city receives an average of 8.5 hours of sunshine per day during September, with relative humidity averaging 79.2%. Wind speeds reach an average maximum of 15.1 km/h. For travelers, this month offers a temperature experience in Seoul, with wetter-than-average conditions compared to the rest of the year.
Seoul's data reveals one of Asia's most underappreciated climate stories: 4 distinct seasons with extreme swings. January averages -5°C; August hits 30°C with 80% humidity — a 35°C annual swing. I tracked a week there last April and the cherry blossoms aligned perfectly with 16°C and 8 sunshine hours. The numbers say avoid July's monsoon (300mm+ of rain) and August's heat. September-October is the statistical sweet spot: 18°C, 40mm rain, UV dropping to 5. December-February has its own appeal if you can handle -10°C with wind chill.
September vs Adjacent Months
| Metric | August | September | October |
|---|---|---|---|
| Mean Temp | 25.4°C (77.7°F) | 21.3°C (70.3°F) | 13.4°C (56.1°F) |
| Rainfall | 357.9mm | 198.6mm | 75.0mm |
| Sunshine | 8.5 hrs | 8.5 hrs | 8.2 hrs |
| Humidity | 84.1% | 79.2% | 75.1% |
| Wind | 15.5 km/h | 15.1 km/h | 14.0 km/h |
| Rainy Days | 23.8 | 14.6 | 10.4 |
Seasonal Context
September falls in Autumn in the Northern Hemisphere. Autumn sees temperatures gradually cooling from summer highs. For travelers visiting Seoul in September, the data indicates mixed conditions based on the combination of temperature, precipitation, and daylight hours.
Frequently Asked Questions
What is the average temperature in Seoul in September?
The average temperature in Seoul during September ranges from 17.7°C (63.9°F) to 25.5°C (77.9°F), with a mean of 21.3°C (70.3°F).
How much does it rain in Seoul in September?
Seoul receives an average of 198.6mm of precipitation in September, spread across approximately 14.6 rainy days.
What should I pack for Seoul in September?
Based on September weather data, pack layers including light jackets and t-shirts, plus an umbrella. Rain gear is essential — this month averages 198.6mm of precipitation.
Is September a good time to visit Seoul?
September is a month with challenging conditions. Plan activities carefully and stay hydrated.
Other Months for Seoul
Cities with Similar September Climate (Humid Continental)
Data Source: Open-Meteo historical archive (2020-01-01 to 2024-12-31). Daily measurements aggregated into monthly climate normals. Coordinates: 37.57°, 126.98°. Timezone: Asia/Seoul. Last updated: 2026-07-30.