LIMITED POWER OF ATTORNEY FOR SECTION 16 REPORTING OBLIGATIONS


      The undersigned hereby constitutes and appoints each of Michael D. Grover
and Sonia M. Dumbleton as the undersigned's true and lawful attorney-in-fact,
and grants each of them full power to act on behalf of the undersigned and in
the undersigned's name, place and stead, for the purpose of completing and
signing, on behalf of the undersigned, any Form 3, Form 4 or Form 5 (including
any amendments thereto) required or permitted to be filed by the undersigned
pursuant to Section 16 of the Securities Exchange Act of 1934, as amended (the
"Exchange Act"), with regard to the undersigned's holdings of or transactions in
the securities of Financial Institutions, Inc., and to file such forms (and
amendments thereto) with the Securities and Exchange Commission, and to do and
perform each and every act and thing requisite or necessary to be done in
connection with such forms (and amendments thereto,) as fully and to all intents
and purposes as the undersigned might or could do in person.

      The authority of Michael D. Grover and Sonia M. Dumbleton under this
Limited Power of Attorney shall continue until the undersigned is no longer
required to file forms under Section 16(a) of the Exchange Act with regard to
the undersigned's holdings of or transactions in the securities of Financial
Institutions, Inc., unless earlier revoked by the undersigned in writing.

      The undersigned acknowledges that Michael D. Grover and Sonia M. Dumbleton
are not assuming any of the undersigned's responsibilities to comply with
Section 16 of the Exchange Act.


/s/ Justin K. Bigham
Signature
Name:  Justin K. Bigham
Date:  April 1, 2019