I just finished a X-C tour and I was crossing the Midwest during the heat wave around July 4. I managed to ride a century on each of two 100+ degree days, but usually limited myself to around 60 or 70 mpd. On the long days, I'd get up predawn and try to ride 40 by 9:00, temps (and dew points) still in the 70s, take a break, and ride another 20 or 30 by noon and then hunker down in A/C comfort (library, cafe, market, repeat) until early evening. Then I'd ride until dark for another 30 or 40 miles. Sleeping would be a big issue--getting into a tent on a 90-degree evening isn't much fun. Luckily I had a good SW breeze during the whole heat wave. I would camp on a hill and pitch the tent facing the breeze, which would make it possible to sleep.