No, that place was an oven every single time I went. France doesn’t do AC in the majority of (public) places, and they have really good weather during Summer, so it’s 30+°C inside trains, stations, convention centers, restaurants, etc. I don’t mind the heat, but diapers would make it more uncomfortable. (and I’m glad that I don’t mind the heat, because I’m in good health. If my health was bad, for sure I’d struggle in that kind of heat). Though, still, it’s unfortunate that it tends to be so hot during that convention; people are sluggish and less energetic, or they’ll skip wearing a cosplay.