I would stay south for warmer weather...granted you will also be putting yourself in tornado alley as well. Just find a start point and a finish point and start hooking up points for overnight stays in between. No reason to follow an established route, make your own and go ride it.

Why not something like Savannah to San Diego. Go through southern GA/Birmingham/Nacodoches area to get across the deep south instead of sticking WAY south. Create your own route and go ride it.