We ride rain or shine. You need to bring a good rainsuit with you if you are going by motorcycle. In addition to warding off the rain, rainsuits can be quite effective as a wind breaker in cold weather. Believe it or not, you can still have a good time riding in the rain. You just need to be more careful and tone down the speed a bit. Plus in the mountains, there is a good chance that once you get over the next pass you’ll be into dry weather.
Rain is one of the reasons we try to keep the hotels approx. 4 hours apart. On a sunny day you might get there a little quicker. On a rainy day you can take your time. The Alps are the only place that I have been, where I willingly go ride in the rain. It makes a great excuse to increase the frequency of stopping to sample the local coffee shops and bakeries.