Like a prisoner surprised by a chance of escape, Minnesota lakes are hurriedly sawing through the last shackles of winter.

The signature of spring's arrival -- the disappearance of ice from lakes -- is happening up to two weeks earlier than average in many parts of the state. Even sizable lakes near the Canadian border have shed their ice.

The reason is the unusually warm March and an unusual pattern of wintry conditions before that, said assistant state climatologist Pete Boulay.

Lakes in eastern and south-central Minnesota, including Lake Pepin, Lake Calhoun and White Bear Lake, went ice-free in recent days, following the fourth-warmest March on record and a winter with (surprise!) about three-quarters the normal dose of snow in the Twin Cities. Though Lake Pepin's breakup 16 days early might have been aided by floodwaters -- it's a wide spot of the Mississippi River -- White Bear, had no such assist for Thursday's ice-out, 11 days earlier than average.

Two other major metro lakes, Minnetonka and Waconia, could be declared ice-free Friday. Lake Minnetonka's average ice-free date is April 13. Lake Waconia's is April 12.

In northern Minnesota, where International Falls had its warmest March ever and also three-quarters its normal winter snow, Echo Lake, about half the size of White Bear, lost its ice Wednesday.

Lakes in southwestern Minnesota are still holding theirs, thanks to the state's heaviest snow cover for much of the winter, which kept the region cooler longer, Boulay noted. Southwestern Minnesota is usually where spring warmth first takes hold in the state, but March in Sioux Falls, S.D., the nearest reporting station, was 3.5 degrees cooler than in the Twin Cities.

Jan Holtz Kraemer, who rides a bike around White Bear Lake before making an official ice-out declaration, said that earlier this winter she had picked April 28 as the day the ice would be gone.

"Boy, did I miss it," Kraemer said. "We had a lot of ice."

Bill McAuliffe • 612-673-7646