September is one of the most interesting months to visit Korea because the weather gradually transitions from summer heat to early autumn coolness. When travelers search for “Korea weather in september / what to wear in september in Korea,” they often discover that the month begins surprisingly warm and slowly becomes much more comfortable toward the end. Early September can still feel like late summer, while the last week often brings crisp mornings and cooler evenings.
In general, daytime temperatures during the first half of the month often remain above 30°C (86°F) in many cities, especially in inland areas. However, regular rain systems and seasonal weather changes begin to lower temperatures gradually. By late September, many regions experience pleasant highs in the mid-20s°C and noticeably cooler nights.
Because of these shifts, packing for Korea weather in september / what to wear in september in Korea requires some flexibility. Lightweight summer clothing is still useful in the first half of the month, but a thin jacket, cardigan, or windbreaker becomes very helpful as mornings and evenings turn cooler. Travelers should also carry a compact umbrella since rainfall can occur frequently during early autumn weather patterns.
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Click on the city you’re curious about to see the September weather.
Korea weather in September – Seoul
Seoul is located in the northwestern part of South Korea and experiences a continental climate influenced by inland air masses. While September technically marks the beginning of autumn, early parts of the month often retain summer heat due to the urban heat island effect created by dense high-rise buildings. As rain systems move across the peninsula, temperatures begin to cool more noticeably during the second half of the month. By late September, the city usually starts feeling fresh and comfortable.
Week 1
Early September still felt like summer in Seoul. The highest temperature reached 33.0°C (91.4°F), while the lowest temperature stayed around 22.0°C (71.6°F). Several rain events brought about 20.4mm to 44.2mm of rainfall across the city. Despite the rain, the air remained warm and slightly humid during most afternoons.
Week 2
Temperatures began to soften slightly during the second week. The highest temperature reached 31.7°C (89.06°F), while the lowest dropped to 18.4°C (65.12°F). Around 63.7mm of rain fell during a strong rainfall event late in the week. The combination of rain and cooler nights started to hint at the arrival of early autumn.
Week 3
Mid-September brought a mix of warmth and frequent showers. The highest temperature reached 30.7°C (87.26°F), while the lowest fell to 17.5°C (63.5°F). Several rainy days produced around 35mm to 52mm of rainfall during passing weather systems. Travel conditions felt humid but noticeably more comfortable than the first week.
Week 4
Late September clearly marked the seasonal shift. The highest temperature dropped to around 27.3°C (81.14°F), while the lowest temperature cooled to 16.6°C (61.88°F). Intermittent rain events brought roughly 35mm to 44mm of rainfall during the week. The overall atmosphere felt fresh, signaling the real beginning of autumn in Seoul.
Week 5
The final days of September continued the cooling trend. The highest temperature stayed around 24.0°C (71.42°F), while the lowest temperature hovered near 16.5°C (61.7°F). Only light rainfall of around 10mm appeared toward the end of the month. The city felt comfortable for sightseeing, especially during the pleasant evenings.
Summary & What to Wear in august in Korea (Seoul)
September in Seoul begins warm but gradually becomes cooler and more refreshing. Early weeks still require summer clothing, while later weeks feel much closer to autumn. Travelers should pack breathable shirts, comfortable walking shoes, and a light jacket for evenings. A small umbrella is also useful because rain showers are common during early fall weather systems.
Korea weather in September – Gangneung
Gangneung lies along Korea’s eastern coastline facing the East Sea. The nearby mountains influence weather patterns, often causing sudden rainfall when moist air moves inland. Coastal winds can sometimes moderate temperatures, but late-summer heat can remain strong during early September. Heavy rain systems occasionally develop due to coastal weather interactions.
Week 1
The first week felt intensely warm along the coast. The highest temperature reached 34.8°C (94.6°F), while the lowest temperature stayed around 22.1°C (71.8°F). Only light rainfall of about 4.6mm appeared during passing showers. The weather felt sunny and bright but noticeably hot for early autumn.
Week 2
Temperatures began to moderate slightly. The highest temperature reached 32.0°C (89.6°F), while the lowest temperature dropped to 17.6°C (63.68°F). A powerful rainstorm delivered about 103.7mm of rainfall during a single day. The rain temporarily cooled the air and refreshed the coastal atmosphere.
Week 3
Another round of intense rainfall arrived during mid-September. The highest temperature reached 31.7°C (89.06°F), while the lowest temperature dropped to 16.8°C (62.24°F). Heavy rain events delivered between 83mm and 88mm of precipitation. Travel conditions felt humid but dramatically cooler after the storms.
Week 4
The late-month weather became calmer. The highest temperature dropped to 28.8°C (83.84°F), while the lowest temperature reached 15.7°C (61.52°F). Light rainfall around 10mm to 14mm occurred during scattered showers. The coastal breeze made outdoor activities much more pleasant.
Week 5
The final days of the month felt noticeably autumnal. The highest temperature reached 25.4°C (77.72°F), while the lowest temperature stayed near 15.3°C (59.54°F). Rainfall remained minimal at around 8mm. Walking along the beach felt refreshing compared to the intense heat earlier in the month.
Summary & What to Wear in august in Korea (Gangneung)
Gangneung experiences a dramatic shift from late summer heat to cooler coastal weather during September. Early weeks remain very warm, while mid-month storms bring heavy rainfall and cooler air. Lightweight clothing works best during the first half of the month. Travelers should also bring a waterproof jacket or umbrella due to the possibility of sudden coastal rainstorms.
Korea weather in September – Gyeongju
Gyeongju is located in the southeastern inland region of Korea and is surrounded by low mountains. This basin-like geography often traps warm air, making daytime temperatures feel hotter than nearby coastal areas. As autumn approaches, the region experiences large temperature differences between day and night. September therefore combines lingering summer heat with noticeably cooler evenings.
Week 1
Early September remained very warm across the historic city. The highest temperature reached 34.7°C (94.5°F), while the lowest temperature stayed around 22.6°C (72.7°F). A rainfall event brought about 12.0mm of precipitation early in the week. Walking through outdoor heritage sites still felt quite hot during midday.
Week 2
The weather began to fluctuate more noticeably. The highest temperature reached 30.8°C (87.44°F), while the lowest temperature dropped to 17.5°C (63.5°F). Rainfall totaling around 39.7mm occurred during passing weather systems. The evenings felt much cooler compared to the first week.
Week 3
A brief return of summer warmth appeared during the third week. The highest temperature reached 34.1°C (93.38°F), while the lowest temperature stayed near 18.0°C (64.4°F). Rainfall remained light at around 10mm for the week. The sunny conditions made historical sightseeing feel warm but manageable.
Week 4
Late September finally brought cooler autumn air. The highest temperature reached 29.2°C (84.56°F), while the lowest temperature dropped sharply to 15.8°C (60.44°F). Only minimal rainfall occurred during this period. The large day-night temperature difference became noticeable for travelers.
Week 5
The final week continued the cooling trend. The highest temperature stayed around 27.4°C (81.32°F), while the lowest temperature hovered near 14.0°C (57.2°F). Rainfall remained light at around 8mm. The evenings felt crisp and perfect for visiting night-time attractions.
Summary & What to Wear in august in Korea (Gyeongju)
Gyeongju often feels hotter during the day than coastal cities in early September. However, evenings cool down quickly as the month progresses. Travelers should wear breathable summer clothing during daytime sightseeing. Bringing a light jacket or sweater is helpful for cooler evening walks around historical sites.
Korea weather in September – Busan
Busan sits along Korea’s southeastern coastline and experiences a humid maritime climate. The nearby ocean keeps temperatures slightly more stable compared to inland cities. Because seawater retains heat, Busan often stays warm longer into autumn. September typically brings pleasant beach weather with gradually decreasing humidity.
Week 1
The month began warm and humid along the coast. The highest temperature reached 33.6°C (92.5°F), while the lowest temperature stayed around 24.1°C (75.4°F). Light rainfall of about 6.6mm occurred early in the week. Evenings remained warm due to the influence of the sea.
Week 2
Temperatures remained stable but slightly cooler. The highest temperature reached 33.2°C (91.76°F), while the lowest temperature dropped to 21.6°C (70.88°F). A rain event delivered around 28.7mm of precipitation. The weather felt slightly less humid after the rainfall.
Week 3
Mid-September still felt like late summer in Busan. The highest temperature reached 31.8°C (89.24°F), while the lowest temperature stayed near 20.8°C (69.44°F). Rainfall remained light at around 7.2mm. Beach walks during the evening felt comfortable and breezy.
Week 4
Temperatures began to decrease gradually. The highest temperature reached 30.2°C (86.36°F), while the lowest temperature dropped to 19.0°C (66.2°F). Rainfall remained minimal during this period. Outdoor travel conditions became noticeably more pleasant.
Week 5
Late September felt like early autumn near the coast. The highest temperature reached 27.9°C (82.22°F), while the lowest temperature dropped to around 19.0°C (66.2°F). Rainfall remained light at roughly 6mm. The sea breeze made evening walks along the beach very enjoyable.
Summary & What to Wear in august in Korea (Busan)
Busan stays warmer longer than many inland cities during September. Summer clothing remains comfortable for most of the month, especially during daytime activities. However, evenings can become slightly cooler near the ocean. Packing a light shirt or thin jacket is usually enough for late-night seaside walks.
Korea weather in September – Jeju
Jeju Island sits south of the Korean peninsula and has a mild maritime climate influenced by subtropical weather patterns. Because of its southern location, the island often remains warm even when mainland cities begin cooling down. Rainfall can be frequent due to seasonal weather systems and occasional typhoons. The island’s strong winds also play a major role in shaping local weather.
Week 1
Early September remained extremely warm across the island. The highest temperature reached 34.6°C (94.3°F), while the lowest temperature stayed near 25.4°C (77.7°F). Light rainfall occurred during passing showers totaling about 10mm. The humid air made afternoons feel tropical.
Week 2
Temperatures remained high but storms developed across the region. The highest temperature reached 34.9°C (94.82°F), while the lowest temperature dropped to 23.4°C (74.12°F). Heavy rainfall events delivered around 40mm to 44mm of precipitation. The rain temporarily cooled the air but humidity stayed high.
Week 3
Warm weather continued through mid-September. The highest temperature reached 34.1°C (93.38°F), while the lowest temperature stayed near 22.0°C (71.6°F). Rainfall around 42.4mm occurred during passing weather systems. Travel conditions felt warm but manageable with ocean breezes.
Week 4
The island slowly began cooling down. The highest temperature reached 32.6°C (90.68°F), while the lowest temperature dropped to 21.3°C (70.34°F). Heavy rainfall around 94.4mm occurred during a strong storm event. The rain created dramatic skies and cooler evenings.
Week 5
Late September felt slightly milder across Jeju. The highest temperature reached 30.0°C (86°F), while the lowest temperature hovered around 20°C (68°F). Rainfall remained moderate at roughly 15mm. The island atmosphere felt warm but far less intense than midsummer.
Summary & What to Wear in august in Korea (Jeju)
Jeju stays warm and humid for most of September due to its southern location. Summer clothing remains comfortable for sightseeing and coastal drives. Because rainfall can occur suddenly, bringing a lightweight rain jacket is very useful. Breathable clothing and comfortable walking shoes are recommended for exploring the island.
This has been Seoul Mate Lenny, sharing a closer look at Korea’s weather across different cities. I hope this guide helps anyone planning a trip to Korea better understand the climate and prepare for their journey.