Forget about prevailing westerlies. The surface winds in the middle of the country will most likely be out of the Southeast by June. In July we had a headwind the entire way across eastern Colorado and Kansas (the portion of the trip where winds mattered the most because they are open plains). Look at these graphics to see what i mean.
If going again. I'd be inclined to go east to west if starting in April, May, or June. That way you avoid some of the heat and humidity in the East and also avoid possible snow in the Rockies. The later you go the more sense a start in the west makes.
The factors that made a start in the west best for us were
- The worst climbs are in Virginia. Strange but true. There are long climbs in the West, but they are all fairly gradual. Not only that but Virginia has more total elevation change than any other state on the route. Since two of us had not had time to train before the trip we wanted to put off the steep climbs. This made training as we went much more palatable.
- We liked the idea of having air travel out of the way up front.
- We liked the idea that it would be harder to back out and quit after a week.
- It was awesome that family could meet us at the finish, throw us a big picnic, and drive us home.