South Korea Seoul Weather in September — Climate Guide
September in Seoul is Good
Seoul Weather in September — Quick Answer
As of 2026- Avg temp
- 27° / 17°
- Rainfall
- 165mm · 10 days
- Crowds
- Busy
As of 2026, Seoul in September averages a high of 27°C and low of 17°C with 165mm of rain over about 10 days. Short sleeves + light cardigan. Daytime mild (24-27°C), evenings cooler (17-19°C). Crisp Korean autumn light begins late month.
September is Good for Seoul.
September is Seoul's transition into autumn. Early September still has summer humidity (70%+, 26-29°C / 79-84°F). Late September dramatically cools — daily highs drop to 23-25°C / 73-77°F with low humidity.
Chuseok (Korean Thanksgiving) is THE major event — varies year to year (typically late September or early October). The 5-day national holiday sees Seoul's residents travel to ancestral hometowns. Many small restaurants close. Trains and KTX bullet trains are 100% booked weeks ahead. If your dates align with Chuseok, expect closures but also experience traditional Korean culture (palaces and museums offer special programs).
Travel score
Early autumn + avoid Korean Chuseok week
September Weather at a Glance
September averages 79°F / 26°C highs and 61°F / 16°C lows — summer's tail. Humidity drops to 65%, daylight shortens (sunset 7:00 PM → 6:00 PM). Autumnal equinox around September 23. Typhoon season peaks (1-2 storms per month) — track JMA and Korean Meteorological Administration. 9 rainy days.
September Travel Advice
Short sleeves + light cardigan. Track typhoon warnings — storms close trains and outdoor venues 24-48 hours after warning. Korean Chuseok (varies by year, mid-September to early October) 5-day holiday is Korea's biggest — 60-70% of restaurants close, KTX and flights spike 2x. Late September brings the first foliage announcements.
Flying In from Overseas
Korean Chuseok dramatically spikes domestic travel ($230+ round-trip Incheon-Jeju, $115+ KTX Incheon-Busan). Post-Chuseok week is the year's best value window. International fares stay near $300-500 round-trip from Tokyo.
September Pricing Trends
Chuseok week hotels 1.5-2x baseline: Gangnam 4-star $170-310/night. Post-Chuseok week returns to $140-220/night.
Seoul September Weather Stats
Avg High
27°C
Avg Low
17°C
Rainy Days
10
165mm total
Sunshine
6.5h
Daily avg
Humidity
72%
Comfortable
UV Index
7
High
Wind
11 km/h
Gusts 22
Crowds
Busy
At attractions
September Sunrise & Sunset
Air Quality
PM2.5
25 μg/m³
PM10
38 μg/m³
Status
Moderate
Feels-Like Temperature & Wind
Feels like
Daytime
30°C
Nighttime
18°C
Humidity and wind affect how the actual temperature feels.
Wind
11 km/h
Max gust 22 km/h
Activities Recommended for September
September Travel Pros & Cons
Pros
- Late September weather genuinely improves
- Chuseok cultural experience (if dates align)
- Korean Music Festival season
Cons
- Typhoon season — flight risk real
- Chuseok closes many businesses
- Hotel prices climb toward October peak
September Events & Festivals
- Chuseok (Korean Thanksgiving) — major holiday, varies year to year (typically late September)
- Typhoon season peaks early-to-mid September
- Korean Music Festival season begins
Seoul in September — Full Picture
September is Seoul's transition into autumn. Early September still has summer humidity (70%+, 26-29°C / 79-84°F). Late September dramatically cools — daily highs drop to 23-25°C / 73-77°F with low humidity.
Chuseok (Korean Thanksgiving) is THE major event — varies year to year (typically late September or early October). The 5-day national holiday sees Seoul's residents travel to ancestral hometowns. Many small restaurants close. Trains and KTX bullet trains are 100% booked weeks ahead. If your dates align with Chuseok, expect closures but also experience traditional Korean culture (palaces and museums offer special programs).
Typhoon season peaks early-to-mid September. Direct hits on Seoul are rare but train suspensions and flight cancellations happen. Buy refundable airline tickets and check NHK World news + Naver weather daily during your trip.
Korean Music Festival season begins. Major K-Pop concerts and festivals (CJ ENM Awards, Seoul International Music Fair) happen September-October. Tickets often sell out 2-3 weeks ahead.
Late September weather is genuinely the start of Seoul's golden window. Hotel prices climb back toward peak rates but value remains good in early-mid September before the autumn foliage rush.
What to Wear & What to Pack
Short sleeves + light cardigan. Daytime mild (24-27°C), evenings cooler (17-19°C). Crisp Korean autumn light begins late month.
Packing Checklist
Seasonal Weather Overview
Spring (Mar·Apr·May)
17.3°C
7°C
8/mo
Summer (Jun·Jul·Aug)
29.7°C
20.7°C
13.3/mo
Autumn (Sep·Oct·Nov)
Current19°C
9.3°C
7.3/mo
Winter (Dec·Jan·Feb)
3.7°C
-4.7°C
5.3/mo
Seoul Monthly Weather Comparison
| Month | High | Low | Rain | Sun | Humid | UV | Crowd | Price |
|---|---|---|---|---|---|---|---|---|
| 2° | -6° | 6d·21mm | 5.5h | 60% | 2 | Quiet | Low season | |
| 5° | -4° | 5d·23mm | 6h | 58% | 3 | Quiet | Low season | |
| 11° | 1° | 7d·49mm | 7h | 58% | 4 | Moderate | Shoulder | |
| April (Best) | 18° | 7° | 8d·70mm | 7.5h | 60% | 6 | Very busy | Peak |
| May (Best) | 23° | 13° | 9d·105mm | 8h | 64% | 8 | Busy | Peak |
| 28° | 18° | 10d·130mm | 7.5h | 70% | 9 | Moderate | Shoulder | |
| 30° | 22° | 16d·405mm | 4.5h | 78% | 9 | Moderate | Shoulder | |
| 31° | 22° | 14d·290mm | 5.5h | 75% | 9 | Busy | Peak | |
| 27° | 17° | 10d·165mm | 6.5h | 72% | 7 | Busy | Peak | |
| October (Best) | 19° | 9° | 6d·50mm | 7h | 65% | 5 | Very busy | Peak |
| 11° | 2° | 6d·50mm | 6h | 65% | 3 | Moderate | Shoulder | |
| 4° | -4° | 5d·22mm | 5h | 65% | 2 | Moderate | Shoulder |
View Other Months
Seoul September Hotel Picks
Frequently Asked Questions
Is September a good time to visit Seoul?
Seoul in September is Good. Tourist crowds are busy and flight/hotel prices are peak.
What's the average temperature in Seoul in September?
Seoul September averages a high of 27°C and a low of 17°C.
Does it rain much in Seoul in September?
Seoul September averages 165mm of rainfall over about 10 rainy days.
What should I wear in Seoul in September?
Short sleeves + light cardigan. Daytime mild (24-27°C), evenings cooler (17-19°C). Crisp Korean autumn light begins late month.
What time are sunrise and sunset in Seoul in September?
Seoul September sunrise is 06:09 and sunset is 18:35, with 12h 26m of daylight.
What's the air quality like in Seoul in September?
Seoul September air quality (AQI) averages 60, rated Moderate. PM2.5 averages 25μg/m³.
What activities are recommended in Seoul in September?
In September, Seoul is great for Chuseok cultural experiences, K-Pop concerts, Late-month outdoor walks.
Is September peak season in Seoul?
Seoul September crowds are busy and prices are peak. Advance reservations are strongly recommended.
Best Months to Visit Seoul
View Other Months
Planning a September trip to Seoul?
You've checked the weather — next come the budget and the route.
Why you can trust weather guide
Based in Chiang Mai for 8+ years, with 30+ countries visited across Southeast Asia, Japan, and Europe. Every detail in this guide is primary-source verified as of April 2026, with prices auto-refreshed via live exchange rate APIs. This isn't AI-generated boilerplate — it's written from the perspective of someone who has actually been there.