If Something Goes Wrong

Heat, Cold, Dust & Storms

The four things the weather here can do to a trip, and what to check before each one does.

The short answer

Korea has four distinct seasons and two of them are severe. Summer is hot and wet and ends in typhoon season; winter is properly cold and dry. Spring brings the dust. None of it should change whether you come — it changes what you pack and which afternoons you plan indoors.

Summer, and the rain that isn't drizzle

From roughly late June the rainy season arrives, and it does not rain the way it rains in most places: it falls hard, for hours, and streets flood briefly. Then July and August are hot and humid, which is a different tiredness from dry heat — you will want a mid-afternoon hour somewhere air-conditioned, and everything indoors is air-conditioned.

Carry water and a small umbrella from June onward. Convenience stores sell both at the moment you realise you need them.
Anything outdoors is best early or late; the middle of the day is for museums, cafés and department stores.
Typhoon season runs through late summer into early autumn. A typhoon here usually means a day of very heavy rain and cancelled ferries and flights, rather than danger on the street — but it does mean a plan needs a fallback.

Winter, which is colder than the number suggests

It is dry cold with wind, and the wind is the part that decides whether a day outside is pleasant. The buildings and the subway are heated well, so the pattern is short outdoor stretches between warm places rather than a long cold day.

Layers, and something that stops wind. A coat that works for damp cold elsewhere may not work here.
Cover the ends: hat, gloves, and shoes you can walk a long way in.
Heated floors are normal in accommodation, and are the reason a room can feel warm while the air is cool.

Fine dust

Spring is the season people mean. On a bad day the sky is white rather than blue and the far buildings go soft. Most days are fine; the bad ones are worth knowing about in advance because they are the days to move a hike indoors.

Check the air quality in a weather app before planning a long day outdoors — every Korean weather app shows it, usually as a coloured word.
On a bad day, an ordinary cloth mask does little. The ones sold here for this are labelled KF80 or KF94, and any convenience store or pharmacy has them.
If you have asthma or a lung condition, take the warning seriously and keep your inhaler with you rather than in the room.

Air quality varies enormously by day and by city, so a headline about Korean air is not a forecast for your trip. Look at the number for tomorrow, not at an article from last year.

What actually gets cancelled

Ferries first, then flights — Jeju in particular is weather-dependent. Trains and the subway keep running through almost anything. If your plan has a ferry in it, have a second version of that day.

Emergency alerts arrive as loud phone messages, in Korean, at any hour — for storms, floods and heat warnings. The noise is alarming the first time. Setting them to silent is possible but they are also the fastest warning you will get, so it is a trade worth making deliberately rather than at 6am.