To answer the OP's question, it'll be too hot but i'd still go out. It'd be a novelty for us here to ride in such heat. I did it once or twice about 5 years ago when it hit 90F. My knees felt like they were swelling up and i was peeing sweat (sweaty legs that's a novelty!) but boy was it enjoyable compared to the usual freezing peeing down crap we have to put up with!
I'd like to go for a ride in this supposed 87F we're expecting tomorrow but i'll be saving my legs for Wednesday's club ride. Having said that, i bet i get some miles in if only a few, just to experience some hot weather cycling.