I realize I've only used my mask a few times on IAP but when i did use it, it was for 45 minutes on a sunny day in St-Jean, in the summer. For those of you who have experienced that, you know it's bloody hot. Anyways, as long as the nose cup is fitted properly, you shouldn't have a problem with fogging, I know I didn't. But man, the amount you swear wearing those... but I digress, not a bad mask. I still wear mine when going for runs once in a while.