I've ridden in temps up to 90 degrees here in NC. While I'm aware of the warmth on the left side, it is not uncomfortable. I don't ride in stop and go traffic, so I can't comment on if it's worse then. Anything below about 70 and I don't notice anything at all. In fact, on one 45 degree day when I wasn't wearing long johns or chaps, I was wishing for MORE heat (and yes, lower vents were closed).