LIMITED POWER OF ATTORNEY FOR SECTION 16 REPORTING OBLIGATIONS


      The undersigned hereby constitutes and appoints each of Michael D. Grover
and Justin K. Bigham 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 Justin K. Bigham 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 Justin K. Bigham
are not assuming any of the undersigned's responsibilities to comply with
Section 16 of the Exchange Act.


/s/ Sonia M. Dumbleton
Signature
Name:  Sonia M. Dumbleton
Date:  April 1, 2019