Thick fog enveloped much of Minnesota this morning and caused delays at three Mower County schools districts.

LeRoy-Ostrander, Lyle and Southland schools were two hours late Monday.

The National Weather Service issued a dense fog advisory Monday morning for more than two dozen counties, primarily in the southern half of the state. Visibility was down to a quarter of a mile or less.

The fog also canceled Gov. Mark Dayton’s air travel to a water quality forum. The governor was unable to fly into Luverne.

The Associated Press contributed to this report.