We are visiting relatives in small cities several hours north of Helsinki. Should I take a skirt, a shawl? Should my husband take a tie? Are outlying areas significantly different from Helsinki in style and customs?
Why don't you ask your relatives?
I only have a two trip sample to draw from, both including time in Helsinki and in rural resort areas, and both during winter. Local dress seems to be more "formal" in Helsinki and "sports casual" in the outlying regions. (During winter everyone seems to be dressed alike except for the Russian women in full length furs). I wouldn't bring a tie or anything beyond work casual unless the relatives are planning some kind of grand formal event. Worst case would be a shopping trip to a Merimekko shop.
PS Southwestern US food seems to be the going out dinning preference in Finland. What would you wear to a American Tex-Mex restaurant?