It's not going to be raining the whole time..
it does rain frequently during summer, mid june to july.
in korean, it's called Jangma Season
last summer wasn't that bad at all. it rained once every week or two.
however, it's impossible to predict how the weather is going to be..
and due to global climate changes, the weather has been very wacky everywhere.
and alot of storms hit southern regions of korea and japan past year.
in seoul, it was a little bit windy, but was not affected.
ps.
Monsoon affects most of East Asia.