While these temps are not typical, even in the central USA—like Iowa and Wisconsin—I've ridden through summer temps over 100°F several times, though the nights were usually much more pleasant.
Also, be aware of your personal level of vulnerability in the heat. Some people seem to be immune to heat—with enough water—while others seem like they can dehydrate in a swimming pool with cold drinks in their hands. I have customers that are afraid of heat in the high 70°Fs, and I've seen them nearly pass out. Me, I prefer the modest temps, but can take the heat OK. If the heat is an issue where you roam: shorten your mileage, start early, or light-up your bike and ride at night in sensible areas.
That C&O tow-path is shady and Ohio has a lot of Youth Hostels that might be good layover spots. (See also: HI-USA.)
Yours in Cycling,
Gilbert Anderson
North Road Bicycle Imports P.O. Box 840 166 Courthouse Square Yanceyville NC 27379 milesawhelen@mac.com or cyclestore@aol.com Local: 919-828-8999 or Toll free Nationwide 800-321-5511