Things to Do in Jeju in September

September Weather in Jeju

28°C (82°F) High Temp

20°C (68°F) Low Temp

180mm (7.1 inches) Rainfall

70% Humidity

Is September Right for You?

Advantages

Post-typhoon season stability - September marks the end of Jeju's most unpredictable weather period, with fewer sudden storms and more reliable day planning
Peak silver grass (억새) season begins at Sangumburi Crater and Hallasan slopes - the island's most photographed autumn phenomenon starts mid-September with golden waves visible from 15 km (9.3 miles) away
Tangerine harvest season starts - Jeju's famous hallabong and early mandarin varieties ripen, with U-pick farms offering 30-50% savings over market prices
Optimal diving conditions return - water temperature holds at 23-25°C (73-77°F) with 15-20m (49-66ft) visibility as summer algae blooms clear

Considerations

Lingering typhoon season until mid-September - approximately 15% chance of tropical storm impact requiring 2-3 day itinerary adjustments
High humidity persists at 70-80% making outdoor hiking feel 5-7°C (9-13°F) hotter than actual temperature, especially on Hallasan trails above 500m (1,640ft)
Weekend accommodation prices remain summer-high through mid-September due to Korean autumn holiday travel patterns

Best Activities in September

Hallasan Silver Grass Hiking Trails

September is when Hallasan's famous silver grass (억새) reaches peak beauty. The Gwaneumsa and Seongpanak trails offer spectacular golden grass fields from 1,200m (3,937ft) elevation. Morning temperatures of 15-18°C (59-64°F) make the 9-10 hour summit hike comfortable, while afternoon clouds create dramatic photography conditions. The grass season is short - peak viewing lasts only 3-4 weeks starting mid-September.

Booking Tip: Reserve mountain huts 2-3 weeks ahead for overnight trips. Day hikes require no permits but start before 8am to avoid afternoon weather. Expect costs of ₩30,000-50,000 ($23-38) for guided groups including transport. Book through certified mountain guide services.

Seongsan Ilchulbong Sunrise Tours

September offers ideal conditions for Jeju's most famous sunrise spot. Clear morning skies occur 70% of September days, compared to 40% in summer. The 30-minute climb up the 182m (597ft) volcanic cone is comfortable in 18-22°C (64-72°F) morning temperatures. Women divers (haenyeo) demonstrations happen daily at 1:30pm and 3pm at the base, showcasing traditional diving in optimal water conditions.

Booking Tip: Photography tours with sunrise viewing cost ₩45,000-65,000 ($35-50) including hotel pickup at 4:30am. Book 7-10 days ahead as group sizes limit to 12-15 people. Independent visits cost ₩5,000 ($4) entrance fee.

Udo Island Coastal Cycling

September's moderate temperatures make Udo's 17km (10.6-mile) coastal loop perfect for cycling. The island's peanut ice cream vendors return to full operation, and the famous white sand beaches have 24°C (75°F) water temperature. Ferry crossings run every 30 minutes with minimal wait times compared to summer's 2-hour queues. Afternoon sea breezes keep coastal cycling comfortable despite humidity.

Booking Tip: Ferry tickets cost ₩5,500 ($4.25) round-trip, purchase same-day at Seongsan Port. Bike rentals on island cost ₩15,000-20,000 ($12-15) for 3-4 hours. Electric bikes available for ₩25,000 ($19). Last ferry returns at 5:30pm.

Manjanggul Lava Tube Cave Exploration

September's high humidity makes Jeju's underground attractions especially appealing. Manjanggul Cave maintains 11-21°C (52-70°F) year-round - a refreshing 7-10°C (13-18°F) cooler than surface temperatures. The 1km (0.6-mile) accessible portion takes 45-60 minutes to explore, perfect for midday heat relief. September's lower tourist numbers mean better photography opportunities in the cathedral-like chambers.

Booking Tip: Entry costs ₩4,000 ($3) for adults. No advance booking needed but avoid 11am-2pm when tour buses arrive. Wear closed shoes and bring light jacket - temperature drops significantly underground. Cave tours with geological guides cost ₩25,000-35,000 ($19-27).

Jeju Citrus Farm Experiences

September marks the beginning of Jeju's famous citrus harvest. Early mandarin varieties ripen throughout the month, with U-pick experiences offering fresh fruit at 30-40% below market prices. Family-run farms provide traditional tea ceremonies using citrus peels, and many offer hands-on harvesting experiences. The famous hallabong won't ripen until December, but early varieties are sweeter and juicier than imported alternatives.

Booking Tip: Farm visits cost ₩15,000-25,000 ($12-19) per person including picking experience and 2-3kg fruit to take home. Western district farms offer better prices than tourist-heavy eastern areas. Book 3-5 days ahead for weekend visits during harvest season.

Traditional Market Food Tours

September brings autumn specialties to Jeju's traditional markets. Dongmun Market and Seogwipo Maeil Market feature seasonal preparations of abalone, sea urchin, and fresh-caught cutlassfish. Cool morning temperatures make market walking comfortable, while vendors offer samples of autumn preserves and fermented seafood. Local banchan (side dishes) incorporate September's fresh produce.

Booking Tip: Guided food tours cost ₩40,000-60,000 ($31-46) for 3-4 hour experiences including 6-8 tastings. Independent market visits require ₩20,000-30,000 ($15-23) for substantial meal portions. Markets open earliest at 6am with best selection before 10am.

September Events & Festivals

Mid to Late September

Jeju Hallabong Festival Preparation Season

While the main citrus festival occurs in winter, September marks the beginning of harvest preparation activities at major citrus farms. Visitors can observe traditional farming techniques and participate in early variety tastings that preview the main festival.

Early September

Jeju Women Divers Festival

Celebrating the island's famous haenyeo culture, this festival typically includes diving demonstrations, traditional seafood preparation, and cultural performances. September's optimal water conditions make diving exhibitions particularly impressive.

Essential Tips

What to Pack

Lightweight rain jacket or poncho - September afternoon showers last 20-40 minutes and occur on 40% of days, often starting around 2-4pm

Moisture-wicking hiking socks and extra pairs - humidity at 70-80% keeps feet damp during long walks, especially on Hallasan trails

SPF 50+ sunscreen and lip balm - UV index reaches 8 despite cloud cover, with reflection off volcanic rock increasing exposure

Breathable cotton or linen clothing - avoid polyester which traps moisture in 70% humidity, making outdoor activities uncomfortable

Waterproof phone case - essential for coastal activities and sudden rain showers, especially during boat trips to Udo Island

Light fleece or hoodie - temperatures drop to 20°C (68°F) in evenings and can feel cool with sea breezes

Sturdy hiking boots with ankle support - volcanic terrain on Hallasan requires proper footwear for trails above 800m (2,625ft)

Portable umbrella - more versatile than rain jacket for quick market visits and photography during light showers

Electrolyte supplements or sports drinks - high humidity increases dehydration risk during outdoor activities

Quick-dry towel - useful for sudden rain, coastal activities, and managing humidity-induced moisture

Insider Knowledge

Book accommodations on Jeju's western coast (Hangyeong, Hallim) for 20-30% savings compared to eastern tourist zones, with equally stunning coastal access and better sunset views

Visit Hallasan trails on weekdays - weekend crowds can create 30-45 minute bottlenecks at narrow trail sections above 1,400m (4,593ft), especially during peak silver grass season

Shop for citrus at Seogwipo's morning markets before 9am for best selection and prices - afternoon inventory focuses on tourist-targeted pre-packaged options at 40-50% markup

Download the Jeju Tourism Organization app for real-time typhoon updates and attraction closures - September weather can change rapidly, affecting outdoor itineraries with 4-6 hour notice

Avoid These Mistakes

Underestimating Hallasan hiking difficulty in September humidity - the combination of 70-80% humidity and physical exertion makes the summit trail feel significantly harder than elevation suggests

Not checking typhoon forecasts when booking non-refundable activities - September still carries 15% typhoon risk requiring flexible itineraries and travel insurance

Packing only summer clothes without layering options - September evenings and early mornings can feel surprisingly cool at 20°C (68°F) with sea breezes