I agree about having the correct foot ware. I live on a small horse farm, and it was -11c when I went to the barn this morning. About a week ago, we had 46cm of snow and had another 7cm yesterday. We are used to the cold and snow.
I am unsure of what Viking has planned for Koblenz since nothing is listed in shore excursions. We are not doing some of the excursions such as Heidelburg since we have stayed there, and I have little desire to sit on a bus. Our goal is to relax and enjoy.
Yours, Claudia