The highest day temperature in September 2025 was 94°F. The lowest night temperature was 63°F. The average values for day and night temperatures during September were 82.7°F и 70.7°F respectivly.

The average sea surface temperature in September 2025 for Seoul was 79.6°F. The maximum and minimum values were 74.6°F and 84.4°F respectively.

Most of the days in September are sunny but you can also expect cloudy and gloomy days.

Precipitation total in September for Seoul is 4.1 in. It makes september one of the most rainy months of the year.

The average wind speed in September is 4.9 mph. This value is relatively stable throughout the year.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Seoul in September is 8.2 hours.