Korea Typhoon Season (Peak Months, Jeju, Typhoon Warning)

Between 2016 and 2025, twenty-two tropical storms passed within 300 km of Jeju. Not one of them did so in January, February, March, April, May or June. Not one in November or December either.

That is the whole Korean typhoon problem in two sentences. The season is not long, it is not vague, and it is not spread across the year the way it is further south. It is a four-month window with a hard edge on both sides, and almost everything people get wrong about typhoons in Korea comes from not knowing where those edges are.

a mature tropical cyclone seen from orbit

Photographs here are stock images for illustration and are not pictures of the events described.

The Peak Months are August and September

The Korean season runs from June to October, and the storms that matter arrive in August and September. That is the shortest honest version of it.

The reason is steering rather than heat. Storms form far to the south and spend most of their lives moving west. Whether one reaches Korea depends on when it turns north, and that turn is governed by the position of the subtropical high sitting over the Pacific. Through midsummer that ridge sits far enough north and west that storms are pushed into the Philippines, Taiwan and southern China. By late August it has begun to retreat, and the door to the Korean Peninsula opens.

So the peak is not the peak of storm formation. More typhoons form in July than in September. It is the peak of storms being aimed at Korea, which is a different thing and explains why the Korean season is later than the Philippine one despite the same ocean producing both.

October is not empty either. Late-season storms do reach Korea, and because the surrounding air is cooler they often arrive already changing character, which tends to spread the rain over a wider area rather than concentrating it.

waves breaking over a concrete sea defence

How many actually hit, and why the count is argued

You will find two very different numbers for this, and both are printed by serious sources.

The Korea Meteorological Administration frames it this way. Around 25 to 28 tropical cyclones form in the northwest Pacific in a typical year, and two or three of them influence the Korean Peninsula between June and October. Other references put the figure at about seven a year.

Neither is wrong. They are counting different things. The low number counts storms that meaningfully affect the country. The high number counts every system that enters Korea's area of influence, including ones that pass well offshore and produce a windy afternoon in Jeju and nothing anywhere else.

This matters more than it sounds, because it is the reason travel advice about Korea is so inconsistent. One guide tells you typhoons are rare and one tells you to expect several, and they are both quoting a real statistic. If you are planning a trip, the number you want is the low one. If you are planning a fishing business, you want the high one.

The other thing worth holding onto is that a two-or-three-a-year country has no muscle memory. Korea handles storms well institutionally and badly personally, in the sense that most people go years between having to think about one.

Jeju gets it first, and usually gets it worst

Jeju sits about 90 kilometres off the southern coast, directly in the path of anything recurving out of the East China Sea. It is the first Korean land a storm meets and it takes the storm at close to full strength, before the shallow water and the peninsula have had a chance to take anything out of it.

Alongside Jeju, the regions most affected are South Jeolla in the southwest and, less intuitively, Gangwon in the northeast. Gangwon is on that list because of terrain rather than track. The Taebaek range forces moist air upward on the eastern slopes, and the rainfall totals that produces are frequently the worst numbers of the whole event, from a storm whose centre never came close.

That is the general pattern in Korea. The wind story is a southern coast story. The rain story is a mountain story, and it can happen a long way from where the storm actually went.

Seoul is a partial exception in the other direction. It is far enough north and inland that a fully intact typhoon reaching it is unusual, and what the capital typically gets is a weakening system delivering a great deal of rain over a day.

A Typhoon Warning is not about wind alone

Korea uses a two-step system, an advisory and then a warning, and the thing to understand is that the warning has a rainfall route into it as well as a wind one.

On the wind side, the land threshold for a strong wind warning is a sustained 21 metres per second, or gusts of 26 metres per second. That is about 76 and 94 kilometres per hour respectively, and it is the level at which the KMA considers ordinary outdoor activity to have become a problem.

On the rain side, a typhoon warning can be issued when total expected rainfall from the system reaches 200 millimetres. No wind threshold has to be crossed for that.

This is why you can see a typhoon warning in Korea on a day that does not feel especially windy. The alert is describing the storm's whole package, and in Korea the water half of that package causes more of the damage than the wind half does. Landslides and river flooding, not roofs.

The current warning map is published in English at https://www.weather.go.kr/neng/forecast/warning.do and the full threshold table for every advisory and warning type is at https://www.kma.go.kr/eng/weather/forecast/standard_warning_info.jsp

What it means if you have a trip booked

The practical shape of a Korean typhoon is short. One bad day, occasionally two, rather than the multi-day siege that the Philippines or Okinawa can get.

Flights to and from Jeju go first and go in volume, because Jeju is both the most exposed airport and the busiest domestic route in the country. If your itinerary has a Jeju leg in late August, that is the single booking most worth making flexible.

Rail is the reassuring part. The Korean network usually keeps running through a storm with reduced speeds and some cancellations on exposed coastal sections rather than a full stop, which means a domestic plan can often be rescued by moving it onto the ground.

The part people underestimate is the day after. Mountain roads and national park trails close on their own timetable, and in a country where a large share of the tourism is hiking, a cancelled trail is the thing most likely to ruin a specific plan long after the sky has cleared.

If there is one thing to take from the numbers, it is that Korea is genuinely a low-frequency country for this, and that low frequency is exactly what makes the individual events go badly. Places that get hit constantly build the habit into daily life. Places that get hit twice a year send everybody out to work as usual, and then find out which hillside was not going to hold.

Jeju, Gimpo and the flights that actually stop

Korea's typhoon exposure is not evenly spread, and the difference between the south coast and the capital is larger than the map suggests. Jeju sits out in open water on the approach path, and it takes the weather first and hardest. Busan and the south coast follow. Seoul and the Gimpo–Incheon corridor usually get the remains of a system rather than its core, and by then the wind has normally dropped below the level that closes anything.

For a traveller, that geography turns into one practical fact: the Jeju air route is the first thing to break and the last thing to recover. Jeju–Gimpo is one of the busiest air corridors in the world, it runs almost entirely on short-haul domestic aircraft, and those aircraft are the ones that get repositioned away from an approaching storm. When the Jeju route stops, it does not stop for the hours the wind is actually over the island. It stops for as long as it takes to bring the fleet back and clear the backlog, and on a peak-season weekend the backlog is the longer half of that.

The airport itself is rarely destroyed by a typhoon. What closes it is crosswind. Jeju's runway alignment means a storm passing to the west puts the wind across the runway rather than down it, and the crosswind limit is reached well before anything dramatic is happening outside. This is why the island can look perfectly survivable from a hotel window while every departure board says cancelled.

The second-order effect is the ferry network. Jeju, Ulleungdo and the smaller south-coast islands are served by ferries that suspend on sea-state rather than on wind at the terminal, and sea state lags the storm by a day or more. A ferry can stay cancelled on a clear, calm morning because the swell has not gone down yet. Anyone planning an island hop in late summer should treat the ferry as the least reliable link in the chain, not the flight.

Then there is the part that catches people who are not on the coast at all. Korea's serious typhoon damage is frequently rainfall rather than wind, and it lands inland. A weakening system that crosses the peninsula dumps its water on mountain catchments, and the resulting problems are landslides, closed expressways and suspended intercity rail rather than anything an airport would report. If your plan involves Seoraksan, Jirisan or any mountain road in August or September, the forecast that matters is the rainfall total, not the wind speed or the storm's category.

Finally, the timing inside the day. Korean domestic carriers tend to decide the following day's Jeju schedule the evening before, and the notification arrives by app rather than by phone call. If you are going to be asleep or out of signal, check before you go to bed rather than in the morning. The rebooking queue is first come, first served, and it starts the moment the cancellation posts.

When storms actually reach Jeju, counted from the record

Published Korean typhoon climatology usually reports storms that made landfall on the peninsula, which undercounts what a traveller experiences. The table below counts something more useful: every tropical storm or stronger system that came within 300 km of Jeju, whether or not it made landfall anywhere.

Month	Storms within 300 km (2016–2025)
July	5 ■■■■■
August	7 ■■■■■■■
September	7 ■■■■■■■
October	3 ■■■
All other months	0

Twenty-two storms in ten seasons, or about 2.2 a year. The distribution is the useful part: August and September are equal, which is not what most season guides say — they tend to name August alone. October is not empty either, and a first week of October trip is not automatically outside the season. Before July, the record for this window is genuinely zero.

Counts computed for this page from the RSMC Tokyo best track archive published by the Japan Meteorological Agency. Method: every storm of tropical-storm grade or higher whose best-track position passed within 300 km of the reference point, counted once per storm, by the month of closest approach, for the ten complete seasons 2016–2025. Data downloaded 26 September 2026.

Warning systems by region

This page is part of a series that takes each warning system in the western Pacific on its own terms rather than translating them into one another.

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