Hopefully my recent experience can lend some good "hindsight" advice- ie, lots of things we did totally wrong on our trip (3 months around US), and a few we did right...
We traveled in a partial figure-8 from June 2nd till September 20-something, if I remember right, the following is in order of that:
Wisconsin- It's cold and sucks up here. But we do have some good roads in the north, it's beautiful in the spring, and people are super nice

Rains a fair amount in spring.
Michigan is great (though also chilly, heh). Copper Harbor is absolutely worth seeing. I hope to go back soon. Rains a lot in spring.
Montreal is an awesome city. Do NOT miss the poutine at "La Banquise". Again, a bit chilly in spring...
Nova Scotia is lovely, chilly and fogy. Cabot Trail was great, highly recommended. Rains a lot a lot a lot in spring.
Maine is very picturesque...also rainy (seeing a pattern here?)
New York City is fracking mad.
New Jersey (or, "Niew Joizee"), actually has some great, windy, forested paths out in the boonies. Only rained on us a little bit!
All down the east coast to North Carolina...soaked us. Yech. Chilly, too.
Skyline Drive and the Blue Ridge Parkway- Must see! This was a (the?) highlight of the trip. Incredible, sweeping, continuous curves through montains, forests, mists, clouds, fields of wildflowers...all purpose-built for touring. Stays out of cities, goes for...600 miles? Something like that. Just plain fantastic

Weather can be anything from mild to rainy, fairly warm, though it treated us well. Other than one 36-hour stretch of pouring rain, while we sat glumly in our tent
Tennessee- Tail of the Dragon! R.E.S.P.E.C.T. it, or eat it. But ride it, that's for sure! Tons of other good riding out there. Weather was warm, a bit humid, generally good. Finally had some proper BBQ!!!
Kansas- this was a surprise. Figured it would be terrible...flat, boring etc. But oh god the sky...it's so open, and colorful...you'll see. Put some chill music on and just ride all day. Beautiful. Nice and warm in the day, tad chilly at night, no big deal.
Colorado: Meh, fairly warm, in Denver. Had a good time.
Wyoming: clear, but coooold in the mornings. Incredible vistas.
Montana: surprisingly warm, clear, no rain.
Oregon Coast: Cold, rainy, blech.

(okay, that's not fair, we were in a hurry at this point, but just got dumped on the entire time...)
California Coast: SUNSHINE! WHEE! Still a bit chilly though, till you get below San Fran. Even then, the coast can be surprisingly cool. Head into the mountains for warmth. Beware EXTREME wind on the I-5!!
Southern Cali Coast: simply awesome. Zero rain, warm but not hot. Perfect!
Whew, sorry, that's a lot- hope some of it helps you to prepare!