Best be prepared for extreme low temps, as opposed to avg low temps. Also, be prepared to stay warm if it's raining on a cool or cold day, otherwise, that's gonna hurt.
A few years back, NC had a cold front set up along the CNC route and we set the record low temps for 4 straight Oct days in each of the towns we stayed in. Water bottles froze on bikes in Boone, and we left there amidst snow flurries. In Lexington, we slept in an unheated glorified 'chicken shed' (an exhibit shed at the fairgrounds), and it was like 30 degrees with no heat and open to the outdoors. REI sold out of sleeping bag liners. Man, it was bad enuff to ride in the cold, but we had no warm place to sleep, either.
We stopped at WalMart and bought Wells Lamont cotton working gloves to wear over our 1/2 fingered cycling gloves. I saw a recumbent with a windscreen who had frost completely covering the windscreen. Ain't no defrost button on most bikes...no heater, either...
There's nothing like riding thru low areas in the first 10 miles while the pastures are covered with frost. Be prepared, or you just might have a first hand experience at learning to tolerate cold. And if it's both cold and rainy, rut rho, George, what you gonna do now???
So, prepare for cold and rain just in case, and hope for warm...
i also remember the start in boone,as well as in mt airy. the elevation here is a bit less,2200 ft,(i live in fletcher,close to asheville) but one never knows about our fickle mountain weather. and one should always be prepared for any kind of weather on a trip like this,ESPECIALLy rain! it's best to keep a pannier(or set) on your bike, or at least a rack trunk, so you can store gear for different conditions. i ALWAYS bring a warm hat with me, for the times in camp when it may be cool or damp,mornings or evenings, and sometimes sleep in it! don't get so hung up on the weather...it's easy to do that. if you come prepared, the weather shouldn't make one hoot of a difference.
It depends on who you believe! The Weather Channel and Accuweather both give >50% chance for like Thursday and Friday. Our local Piedmont TV weather guys/gals are saying only 20-30%. I tend to trust the locals. Weather Channel always calls to more rain than we ever see. In Winston-Salem, NC we've had <0.25inches for all of September. Looks to remain fairly dry to me. (My 2 cents).
After six CNCs I can only echo the words of caution already laid out.
Weather prediction--particularly in the mountains is not dependable--although it does generally look great in the current 10-day forecast. (One year we had 10% chance of rain for three days but rode under that 10% all day most of all three.) On the opposite end, the weather report for Boone, looked up on the Internet the day before leaving Asheville, was for temps in the 30s that first night. We actually had mid-50s then clearing to beautiful sunshine. You just have to be prepared for anything.