MINNEAPOLIS — General Mills, Inc. said that weak volume performance across its U.S. retail food categories in December and January will affect its third-quarter results, which will be announced March 21.

General Mills currently estimates that 2012 third-quarter adjusted diluted earnings per share for the period ending Feb. 26 will total 54c to 56c. In last year’s third quarter, adjusted diluted e.p.s. was 56c.

Additionally, General Mills revised its fiscal 2012 adjusted diluted e.p.s. guidance to $2.53 to $2.55, down from $2.59 to $2.61.

Adjusted diluted e.p.s. excludes the effects of mark-to-market valuation of certain commodity positions, and integration costs for the Yoplait international acquisition completed July 1, 2011, the company said.