I have received a lot of questions about interview attire; I have two rules to guide applicants:
1. Do not be noticed for your clothes. You want to be remembered for your accomplishments, not your attire. Years later, I still remember the applicant who arrived in a Bugs Bunny tie. I also recall the applicant who arrived in jeans. (He packed his interview clothes, checked his luggage, his bags were lost, and he had nothing else to wear for his early morning interview. Keep your clothes with you - carry-on.)
2. Be comfortable. No heels that are so high you are in too much pain to take the tour. No coat so light - but stylish! - that you can't walk out of the building.