I'm planning to travel to South Korea with my mom next year. We'll visit Seoul, Busan, and Jeju Island. The timing that works best for us is the last week of May 2025 and the first two weeks of June. Ideally we'd visit when temps are in the mid-70s with the highest likelihood of clear, sunny days.

A lot of the weather info I've found online talks about the monsoon season starting in June, but it's usually referencing late June. I haven't found that much info about early June. How much of a difference is there weather-wise between mid-May and mid-June? Has monsoon season been starting earlier in recent years due to climate change?

I'd like to keep the dates we're currently planning on, but if there's a significantly higher chance of clear, sunny days in May, we may consider moving the trip up a few weeks.

It seems that climate change is driving changes all over the world, so I'm not sure you can get any clear or reliable information about what the conditions will be like in May or June of 2025. That said, I would recommend that you consult weatherspark.com -- it provides an incredibly wide range of climate-related statistics in what I consider to be an easy to use format. I would also encourage you to check it for Seoul, Busan, and Jeju separately, as they are far enough apart to experience different conditions. https://weatherspark.com/

I can say, with certainy, that the temperatures in Jeju in mid-May of 2016 were nearly unbearably hot.

I wonder if you are wedded to the idea of visiting Jeju. IME, it's a haven for those in their late teens and early (very early) 20s -- including (at that time of year) many school groups going to celebrate graduation and/or end of the academic year -- and especially newlyweds in that age range from South Korea, Japan, and China. That's not necessarily a bad thing, but it is IMO something to consider. There are some interesting things to see and experience on Jeju, but with so much to see and do in South Korea, you might want to consider other destinations.

BTW, I loved Seoul and Busan!

If you haven't already seen it, you might want to check my trip report: 4 wonderful solo weeks in South Korea

Hope that helps!

Don't sweat it, literally. You will have a great time. I was in South Korea last week in August and first week of September of 2012. Monsoon season. As we were spending half the time on a driving vacation through the southern half of the country, we got blown off course because of a monsoon. We still had a great time. Instead of immediately going to a coastal town that day, we headed inland and focused on more indoor activities.

I didn't go to Jeju. There's a lot of amazing coastline in Korea. In fact, there is brilliant coastline right in Busan, where the mountains plunge right into the sea. It seems to me that most people miss that. Busan is a microcosm of everything Korean. Though in truth it is not so micro. It can take a long time getting around just using the subway.

Link to my photos. As you can see, we experienced plenty of great weather along with the downpours:

South Korea Photos

@shlemm @kja I think Busan is what I'm looking forward to the most!

I will check out Weather Spark and read your trip report again KJA. I remember reading it years ago, but at the time I wasn't very familiar with Korea. I know more now, so it would be good for me to read it again.

I'm particularly interested in clear weather because we'll be spending a significant portion of the trip near the coast, and the ocean is just so much more beautiful when it's sparking in the sun. Of course we'll have a good time and make the best of it no matter what, but since I'm still in the planning stage, I'd like to make a decision based on the highest likelihood of clear skies.

South Korea typically has more stable weather in late May, with temperatures around 24°C and low humidity, than in early June, when the monsoon season begins and brings with it more rain. Climate change has caused the monsoon season to start earlier, so there may be more sunny days in mid-May than in mid-June.

Hi. We just got back a week ago. Were there the first 2 weeks-Busan and Seoul. Weahter great-jacket needed at times in Busan. Last 2 days in Seoul were very hot-sun so strong by 10 am but cools down nicely by 6 so take a break from 2-5. Seems heat was rolling in by June 9.