Two of my does, who share a cage, have unusually wet chins almost like they've been drooling. They're teeth look like they should and it's really warm outside. I was wondering if this is sweat or something more sinister. Here are some photos...
Rabbits cannot sweat. They have been panting, which means they are not just stressed by the heat but in distress from the heat. You could lose them if you don't cool them down. Frozen water bottles, fans, bring them inside...whatever it takes.