Weather in Seoul for September 2025

In September, Seoul, South Korea, experiences a transition from the hot, humid summer to the cooler, more comfortable autumn season. At the beginning of the month, temperatures typically range from 20° to 28°, with humidity levels still relatively high.

The city often sees occasional rain showers, as the tail end of the monsoon season can extend into early September. These showers can be heavy at times, but they usually become less frequent as the month progresses.

As September advances, the weather starts to cool down. By mid-month, temperatures generally range from 18° to 25°, and the humidity begins to drop, making the air feel fresher and more pleasant. The skies often clear up, providing more sunny days and less precipitation.

This period is ideal for outdoor activities and exploring the city's numerous parks and historical sites.

By the end of September, the temperatures further decrease, ranging from 15° to 22°. The nights become noticeably cooler, and the crisp autumn air starts to set in. The likelihood of rain diminishes significantly, and the city enjoys more stable weather conditions.

The changing foliage begins to add vibrant colors to the landscape, making late September a picturesque time to visit Seoul.