When I was in Nagoya last year in Sept., It was pretty hot and humid as well. I wasn't used to it, and there were days when I would sweat even when I was just standing still.
But I did a lot of walking, so imagine how much more sweat that produced. Ok, don't!
Learned quite quickly that I needed to carry one of those personal towels/napkins/handkerchief to wipe off the sweat.