Silk, being a natural fabric, breaths decently depending on the weave. Satin is a tight weave, and heavier, so it will breath the least. Taffeta is also a very tight weave (if good quality), so it won't technically breath much more, but there's less weight so heat at least escapes. Going downhill, shantung is next, it has some slubs and uneven weaving, making it looser. Dupioni is known for it's slubs and loose weave. Chiffon, not surprisingly, is the lightest silk.
My biggest tip is to check the lining more than worry about the outside. Most wedding gowns, in order to save money forgo a good lining, some don't even use polyester (which is decent depending on the quality), but go with cheaper man-made fabics. They don't breath and they don't absorb moisture well. If you have a man-made fabric lining, you can find something you can put underneath at least part of it that's made for exercise or wicking away moisture. Or sew pieces in where you normally sweat (like cups or a small pad under the arm).
