Jeju (Jeju Island) sää — syyskuu

Regulars are specific the real rainy season here usually doesn't start until the very end of this month, late May and early June instead typically bringing warm, not-too-hot days, though the water itself stays genuinely cold this early. Our row backs that warm, genuinely wet read, 25.7C reading as a hot 29C, over 20C nights feeling 22C, with a substantial 170.2mm of rain across 11 days and humidity at 87 percent. Regulars are consistent island weather here stays genuinely changeable day to day, constant strong winds a real factor that keeps conditions feeling cooler than the same heat would inland in Seoul. Evenings cool off noticeably even after a genuinely hot, humid day. The sea sits at a cool 21.9C. The record: 8.6 hours of sun, an 18.6 kph wind and AQI 68.

Jeju-forum threads on January weather agree it's the coldest month, crisp and chilly with a real chance of snow, though posters are quick to note the island rarely drops below freezing the way mainland Korea does this time of year - Seoul's winter is a different, harsher animal entirely. Wind is the recurring theme across threads, strong enough most days that it registers as the defining discomfort more than the raw temperature. Regulars call the occasional severe event genuinely rare rather than typical - one poster recalls a three-day blizzard that shut everything down, but stresses it was an outlier. The upside repeated across threads: crisp air, thin crowds, and volcanic coastal scenery some call more striking under grey winter skies than summer haze. The record: 9C days feeling like a raw 4C, 4.1C nights, 71mm across 10.4 days, 8.3cm of fresh snowfall, a 16.6C sea and wind averaging over 28 km/h - the windy, chilly month the forum describes.

Jeju-forum threads comparing July to August sit July squarely inside the monsoon, or jangma, with one regular describing the rainy season as mainly a June event before warning newcomers to just prepare for warm, humid weather through July and August regardless. Early July is typically the wettest stretch, precipitation arriving in intense bursts rather than all-day drizzle - mornings tend to run clearer, afternoons stormier. The payoff for waiting: late July is called the sweet spot, when the monsoon often breaks and leaves the island lush and green between showers, the beaches warm and inviting. The record backs the intense-burst pattern: 30.1C days feeling like a sticky 36C, 25C nights, 169mm across 12.5 days, 87 percent humidity, 8.9 hours of sun and a 26.1C sea.

May is the month Jeju regulars choose over June: the weather is better, and the Korean summer holidays have not started, so the island is much quieter. Late May leans more towards summer than spring, warm and occasionally hot, and the qualification they always add is that this is a windy, foggy island - mornings and evenings can feel chilly even in a warm week, so a light jacket travels. Our row gives 22.5C days and 15.5C nights with a 20 kph wind. The thing to know before booking a beach holiday is that the beaches do not open until after mid-June; you can sunbathe in May, but the water is cold, our row putting it at 17.9C. The record: 9.3 precipitation days carrying 104.6mm, humidity 80 percent and 9.5 hours of sun.