Great Lakes ice cover, winter 1968-69

"Twenty-three ice charts were produced from data collected on eight reconnaissance flights made during the 1968-69 winter ice season. Ice formation was first reported on December 9, 1968. Areas reporting extended from Duluth, Minnesota, on western Lake Superior, to Barcelona, New York, on the south shore of Lake Erie. Winter temperatures generally varied from slightly above normal in the Lake Superior region to slightly below normal on Lake Erie. During the period of maximum ice cover, 40 percent of the surface of Lake Superior was covered. More than half the ice was concentrated in the Apostle Islands-Duluth-Isle Royale areas at the western end of the lake. Lake Michigan was 15 percent covered with the ice confined mostly to the north end of the lake and Green Bay. Lake Huron contained a maximum 50 percent ice cover with winter ice in the North Channel, the Straits of Mackinac, and Saginaw Bay. Lake Erie was 80 percent ice covered, with heavy winter ice concentrated along the southern and eastern shores. The mid-lake area contained brash and small floes. At maximum, Lake Ontario was estimated to be 10 percent covered, with the ice concentrated in the northeastern end of the lake. The last report of ice in the Great Lakes was from the Buffalo area of Lake Erie on May 2, 1969."