Korea Weather by Month: Temperatures, Rain and Fine Dust

Korea has four distinct seasons, and two of them are difficult. Summer is hot, humid and extraordinarily wet. Winter is cold and dry, with a wind off the Asian landmass that makes it feel colder than the number suggests. Spring and autumn are genuinely excellent and genuinely short.

The figures below are Seoul’s 1991–2020 climate normals, the official 30-year averages published by the Korea Meteorological Administration. Seoul sits in the middle of the country; Busan and the south coast run several degrees warmer in winter, and Jeju warmer still.

The year in one table

The number that explains Korean summer

June, July and August together deliver 892 mm of rain — about 63% of the annual total. Winter, by contrast, gets 68 mm across three months, roughly 5% of the year.

That is the single most useful thing to know before choosing dates. Korea is not uniformly rainy. It is intensely rainy for about ten weeks and comparatively dry the rest of the time. July alone brings 414 mm, more than the entire period from October through March combined.

The heat compounds it. August averages a 30 °C high, but the number that matters is the average low of 22.9 °C. Nights do not cool down. When the overnight low stays at or above 25 °C, Korea calls it 열대야, a tropical night, and Seoul gets stretches of them in late July and August. Air conditioning is not optional in that window.

장마, and why it is not the whole story

Korea’s rainy season, 장마, is a monsoon front that moves north across the peninsula. The 30-year normal dates:

The mistake visitors make is treating the end of 장마 as the end of the rain. Look at the table again: August still delivers 348 mm after the front has moved on. What changes is the character of it. 장마 rain tends to be prolonged and grey; August rain arrives as concentrated downpours, often from convective storms or a passing typhoon. Both months are wet, in different ways.

Fine dust is a winter problem, not a spring one

This is the part almost every travel guide gets backwards. Fine dust is widely described as a spring phenomenon, tied to yellow dust blowing in from the Asian mainland.

The measurements say otherwise. Over recent years, 91% of Seoul’s days exceeding 50 µg/m³ of PM2.5 fell between December and March. That is why Korea’s seasonal management programme, which tightens emissions controls, runs from 1 December to 31 March rather than through the spring.

Spring is not clean — March in particular gets both the tail of the winter accumulation and yellow dust events on top of it — but the worst concentrations cluster in the cold months, when still air and heating emissions combine. If you are sensitive, the months to watch are December through March, with March the sharpest.

Typhoons

Korea is affected by an average of three to four typhoons a year, arriving between July and September, with August the most frequent month.

September deserves a note. Autumn typhoons are often more damaging than midsummer ones, because they tend to carry both strong winds and heavy rain rather than mainly rain. A September trip is usually fine, but it is the month where an itinerary is most likely to be disrupted by a storm.

Spring and autumn are short, and swing

April and October are the best months to be in Korea, and they behave similarly: April averages a 17.9 °C high against an 8.0 °C low, October a 20.2 °C high against 10.6 °C. That is roughly a 10-degree swing within a single day, and it catches people out. An afternoon that justifies a t-shirt turns into an evening that does not. Layers matter more here than in either summer or winter, when the temperature is at least consistent.

Cherry blossom is the reason many people target April specifically. Seoul’s normal first-bloom date is 8 April, with full bloom around 10 April. The front moves north from Jeju and the south coast, which see blossom roughly two weeks earlier. Warm years pull all of it forward — in 2026 Seoul bloomed on 29 March, ten days ahead of normal — so a trip booked to a fixed date is a gamble.

Choosing when to go

Best: late April to late May, and late September to early November. Mild, comparatively dry, and the two windows Koreans themselves treat as the good part of the year.

Manageable: March, if you accept dust risk and cold mornings. Early June, before the rain front arrives. December, if you want cold and dry rather than cold and wet.

Hardest: mid-July to mid-August, which combines the year’s heaviest rain, the highest heat and overnight temperatures that do not fall. It is also when Korean schools are on holiday, so domestic travel is at its peak. January and February are cold but dry and clear, which many people find easier than the summer.

What this means for packing

Winter needs a genuinely windproof coat rather than a thick one. The average January low of −5.5 °C is not extreme, but the wind off the continent is what people underestimate.

Summer needs the opposite thinking: light, quick-drying clothing, and an umbrella you actually carry rather than one you leave at the hotel. A 414 mm month does not arrive politely spread out.

Spring and autumn need layers for the daily swing, and, in March, an awareness that a fine dust reading can change what you want to do outdoors that day.

FAQ

What is the best month to visit Korea?

Late April to May, or October. Both are mild and dry by Korean standards, and October in particular sits between the end of typhoon season and the start of the cold. Cherry blossom pulls a lot of visitors to early April, but that timing shifts by a week or more year to year.

How hot does Korea get in summer?

August averages a 30 °C high in Seoul. The harder number is the average overnight low of 22.9 °C, since nights that stay warm are what makes the humidity feel relentless. Stretches where the low stays above 25 °C are common in late July and August.

When is the rainy season in Korea?

The 장마 front normally reaches Jeju around 19 June and central Korea around 25 June, clearing about a month later. But August remains very wet after it passes — 348 mm on average — so the rainy period in practice runs longer than 장마 itself.

Is Korean fine dust worst in spring?

No. Around 91% of Seoul’s high-concentration days fall between December and March, which is why Korea’s tightened emissions period runs 1 December to 31 March. March is the worst single month, combining winter accumulation with yellow dust.

Does it snow in Seoul?

Yes, but less than the cold suggests. Winter is Korea’s driest season — December through February total about 68 mm of precipitation, roughly 5% of the year. Snow tends to come in a few events rather than as continuous cover.

How cold is Korean winter really?

January averages −2.0 °C with lows around −5.5 °C in Seoul. That is colder than most of Western Europe but not extreme; the difficulty is the dry continental wind, which makes the perceived temperature considerably lower than the reading.

Planning around the calendar as well as the weather? Korean public holidays covers when the country travels en masse. More in the rest of the Korea guides.

← More guides