Update one month later... (12/26/05)
Cruise control set to 70
mph for 40 miles. Some smooth rolling hills. 2000 feet in altitude. Mid to high 60 degrees. This is what I saw:
Then I drive for another 40 miles at 70, and then the next 15 miles at 62. Mostly flat. 1200 feet in altitude. It's past sunset, but Phoenix is always warmer than Tucson, so temps are pretty much near the same.
The car has over 6K miles on it now.