EXHIBIT 99-A

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of Otter Tail Corporation (the "Company")
on Form 10-K for the period ended December 31, 2002 as filed with the Securities
and Exchange Commission on the date hereof (the "Report"), I, John D. Erickson,
President and Chief Executive Officer of the Company, certify, pursuant to 18
U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, that:

      1.    The Report fully complies with the requirements of Section 13(a) or
            15(d) of the Securities Exchange Act of 1934; and

      2.    The information contained in the Report fairly presents, in all
            material respects, the financial condition and results of operations
            of the Company.


                                           /s/  John D. Erickson
                                           -------------------------------------
                                           John D. Erickson
                                           President and Chief Executive Officer
                                           March 26, 2003


A signed original of this written statement required by Section 906 has been
provided to Otter Tail Corporation and will be retained by Otter Tail
Corporation and furnished to the Securities and Exchange Commission or its
staff upon request.