We have done portions of the Pacific Coast in two different years, both times after labor day. We hit wet weather both times (2008 and 2009). Some pretty heavy showers both times. Having said that I work outside on the Oregon Coast a lot (I'm a forester), and it seems like it rains more in June than in the fall. I pack my raingear anytime I'm working there. I would be interested to see the days of precip statistics for the various months. My perception is that it rains fewer days in the fall, just harder. After Labor day the traffic is noticibly lighter. However, there is still the RV crowd, which is pretty scarry at times. The road shoulders are pretty decent for most of the portion we rode (Lund, BC to Crescent City, CA). The folks above make some good points and it is great almost anytime of the year!