I count September as summer here, so it's still often hot. You might want to bring a couple of masks for each day and swap them every so often. That's what I did at SWW a few weeks ago. It was just too hot to keep the one mask on; swapping helped immensely. The hot and sweaty mask is just blah! Have you looked at Vogmasks? There's a girl in my neighborhood who's immunocompromised and she swears they are the best thing ever. The microfiber ones are supposed to be at the NIOSH 95 or 99 standards. I haven't tried them out myself yet but they look pretty cool.