EXHIBIT 5-A


                       [Dorsey & Whitney LLP Letterhead]



Otter Tail Corporation
215 South Cascade Street, Box 496
Fergus Falls, MN 56538-0496

        Re:  Registration Statement on Form S-3


Ladies and Gentlemen:

         We have acted as counsel to Otter Tail Corporation, a Minnesota
corporation (the "Company"), in connection with a Registration Statement on Form
S-3 (the "Registration Statement") relating to the registration under the
Securities Act of 1933, as amended, of debt securities of the Company having an
aggregate initial offering price of $200,000,000 (the "Debt Securities"). The
Debt Securities are to be offered from time to time by the Company on terms to
be determined at the time of the offering and are to be issued under the
Indenture (For Unsecured Debt Securities) dated as of November 1, 1987 (as the
same may be amended and supplemented from time to time, the "Indenture"), by and
between the Company and U.S. Bank National Association (formerly First Trust
National Association), as trustee (the "Trustee").

         We have examined such documents, including resolutions adopted by the
Board of Directors of the Company on June 10, 2002 (the "Resolutions"), and
reviewed such questions of law as we have considered necessary and appropriate
for the purposes of our opinions set forth below. In rendering our opinions, we
have assumed the authenticity of all documents submitted to us as originals, the
genuineness of all signatures and the conformity to authentic originals of all
documents submitted to us as copies. We have also assumed the legal capacity for
all purposes relevant hereto of all natural persons and, with respect to all
parties to agreements or instruments relevant hereto other than the Company,
that such parties had the requisite power and authority (corporate or otherwise)
to execute, deliver and perform such agreements or instruments, that such
agreements or instruments have been duly authorized by all requisite action
(corporate or otherwise), executed and delivered by such parties and that such
agreements or instruments are the valid, binding and enforceable obligations of
such parties. As to questions of fact material to our opinions, we have relied
upon certificates of officers of the Company and of public officials.

Based on the foregoing, we are of the opinion that, when the specific terms of a
series of Debt Securities have been established in accordance with the
Resolutions and Indenture, such series of Debt Securities will have been duly
authorized by the Company and, when executed by the Company and authenticated by
the Trustee as specified in the Indenture and delivered against payment therefor
in


accordance with the Resolutions and the Indenture, will constitute valid and
binding obligations of the Company, enforceable in accordance with the terms of
such series.

         The opinions set forth above are subject to the following
qualifications and exceptions:

                  (a) Our opinions stated above are subject to the effect of any
         applicable bankruptcy, insolvency (including, without limitation, all
         laws relating to fraudulent transfers), reorganization, moratorium or
         other similar laws of general application affecting creditors' rights.

                  (b) Our opinions stated above are subject to the effect of
         general principals of equity, including, without limitation, concepts
         of materiality, reasonableness, good faith and fair dealing, and other
         similar doctrines affecting the enforceability of agreements generally
         (regardless of whether enforcement is considered in a proceeding in
         equity or at law).

                  (c) In rendering the opinions set forth above, we have assumed
         that, at the time of the authentication and delivery of a series of
         Debt Securities, the Resolutions referred to above will not have been
         modified or rescinded, there will not have occurred any change in the
         law affecting the authorization, execution, delivery, validity or
         enforceability of the Debt Securities, the Registration Statement will
         have been declared effective by the Securities and Exchange Commission
         and will continue to be effective, the Indenture and any supplement
         thereto relating to that series of Debt Securities shall have been
         qualified under the Trust Indenture Act of 1939, as amended, and will
         continue to be qualified, none of the particular terms of a series of
         Debt Securities will violate any applicable law and neither the
         issuance and sale thereof nor the compliance by the Company with the
         terms thereof will result in a violation of any agreement or instrument
         then binding upon the Company or any order of any court or governmental
         body having jurisdiction over the Company.

         Our opinions expressed above are limited to the laws of the States of
Minnesota and New York and the federal laws of the United States of America.

         We hereby consent to your filing of this opinion as an exhibit to the
Registration Statement and to the reference to our firm under the caption
"Validity of Debt Securities" contained in the Prospectus that is part of the
Registration Statement.

Dated: June 21, 2002

                                               Very truly yours,

                                               /s/ Dorsey & Whitney LLP


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