Good advice, except I live in a place where temperatures climb above 25-30C(that's 82-86F for you guys across the pond), which makes wearing a jacket really uncomfortable. I also REALLY hate sweat stains on my shirts. Also, as business dress tends to be a bit less formal here(China that is) wearing a jacket when everyone is just wearing a shirt just makes you look awkward.
Get jackets made out of linen or cotton/linen blends. That or lightweight wools with an open weave to let air flow through. I lived in the American South and did just fine with lightweight wools and such year-round (much to the amusement and amazement of friends/colleagues). Even lightweight shirt-jackets would work for you, both functionally and meteorologically.
That or the do the small bag thing.