I am going to be in the area for a week and want to stop by for a day. Are there any days that are worth avoiding for either crowds (Saturday/Sunday?) or for shops closed (Sunday or Monday?)
To avoid the crowds stay away from CT on the weekends. As far as the rest of the days I do not recall a difference. They are crowded anyway. I was just there from a Friday to a Tuesday and I never noticed anything that was closed during the day. Some stores do close late in the day/early evening though.
We stayed in Vernazza from Sunday afternoon until Tuesday morning, in early July, and it was definitely more crowded on Sunday than Monday. And, in Vernazza, there is an outside market on Tuesday mornings.