I was invited by a cast friend to go ride them during a preview last week. If the sun is up and you're in a gondola that doesn't have a screened Disney scene on it, it gets hot very very quickly and becomes uncomfortable fast. If it does have a screened print it gets hot more slowly, but if you're there for more than a minute or two it gets very hot as well. If the wind is blowing while they're stopped there is air circulation and the vents are positioned to keep the air moving and it's really not that unpleasant. If the wind isn't blowing while stopped though it does get stuffy and hot fast. Is it better than a stopped monorail in August? Definitely. As long as they keep them moving they aren't bad at all. It doesn't seem like they used cabins with any sort of UV blocker, but I could be mistaken about that.