I have a Tourmaster textile jacket that I wear in Spring and Fall, and keep the liner zipped in until the temps reach about 70 degrees. From about 70 to 80 I wear the jacket without the liner and with the vents unzipped. But once it gets over about 80 degrees I switch to a mesh jacket to optimize airflow or just wear a t-shirt and take my chances. I have a few lightweight nylon long sleeve t-shirts that I wear in really hot weather, say over 90 degrees. My skin stays covered from the sun but the air goes right through to keep me relatively cool. Of course that means no protection in case I go down, but I accept that as part of the balance between fun and safety. When I see the rider on a sportbike in full racing leathers in 95 degree weather, with a full face helmet and visor down, armored gloves and heavy riding boots, I always think "to each their own, but I would rather not ride than be that miserably hot".