Distance + time+hot/humid=tomorrow

I'm both looking forward to and nervous about tomorrow's ride. It's an 80-miler that is coupled with some of DC's standard summer weather (hazy, hot and humid). We've been pretty spoiled here this summer and I don't know how I'll hold up in this type of heat since I haven't really been training in it much this year. I'm not fond of extreme temps (cold or hot) and I am uncertain about how ready I am for this one. Guess I'll find out...