Timing for My Way Italy tour

Nancy, I took that same tour in early October 2013, and the weather was lovely throughout, and any crowds not overwhelming. September can still be hot, and crowds more plentiful, so my personal recommendation would be to begin as late in September as possible. Great tour by the way, but you will need to plan some of your time in advance, especially for Venice, Florence and Rome, where there are so many choices, and various sites call for advance reservations, and sometimes guided tours.
PS: By the way, I hope you can spend some extra days before and after the tour. There's certainly more to enjoy in Venice, plus you'll want to recover from any jet lag before the tour starts, and of course, Rome wasn't built in a day, and can't be experienced in a day or two either!

Our preference for that part of the world is late September through Oct. We have never run into extended (more than a day) of marginal weather. Generally warm and dry with few showers from time to time.

I agree with Larry and Frank on late Sept/Oct for this trip, especially seeing you are from Oregon. I did the 21BOE in 2014 and was in Venice/Florence/Rome and Monterosso the first week of Sept. It was very, very hot to me. I also did Village Italy at the end of Sept and in to Oct and found weather in Venice and Cinque Terre (the 2 cities I repeated so could compare) much more comfortable for me. I am not sure the crowds were any less later in the month. Those areas are always popular so I would not base it on what you think the crowds might be like.

Thanks so much for your responses. Given your experiences, I think it would be best to push our start date to late September.