Heat makes a big difference for me. In my basement in the low 60s F I am miserable just easy pedaling for 15 minutes if I don't have a fan on. I've got a pair of 20" high velocity fans pointed directly at me (controlled with smart plugs so I can turn them on while riding). Even with both fans blasting I am dripping sweat pretty soon and have to swap out my cotton headband every 20-30 minutes. If I wasn't so lazy I would move the whole setup to the garage where it's colder.