Are there any regulatory requirements regarding temporarily closing a branch due to renovation? Obviously we would put up a sign at the branch ahead of the closing indicating the approximate date of re-opening, but is there any other requirement? We are FRB regulated.

As a state-chartered bank, you should look at anything state law has to say on the question.

Unless you've had previous communications with your state banking commissioner's office, I'd call and ask for guidance. Very likely, they have an informal position on any banking-service related question you may encounter.