Probably a little. More importantly, exercising when it's hotter and more humid means stressing your cardiovascular system more than when it's cool...you will breathe harder, your heart beat faster and your body will overheat more quickly...so it may be good for physical conditioning, as long as you hydrate yourself and are careful with your heart rate. It will not be good for conditioning your other muscles though, since they are working comparatively less hard.
Why not just exercise faster/harder in comfortable clothes? It's give and take.
