The metro area's two biggest lakes have given up their slick flattops for the wavy look.

"Ice-out'' on Lake Minnetonka, a marker that winter is behind us, arrived at 6 a.m. Thursday, according to the Hennepin County Sheriff's Office.

The determination is made when a boat can be piloted through the "narrows" around Big Island and back to the sheriff's water patrol unit in Spring Park.

This method has been used since 1855 for lake boat captains to start the warm-weather navigation season. But the declaration does not mean the lake is completely free of ice.

In the east metro, ice-out on White Bear Lake was declared Wednesday by Jan Holtz Kraemer, who makes the official declaration after surveying the situation from a bike.

Ice out often comes within the first three weeks of April. The date last year was April 2. The earliest came on March 11 in 1878, with the latest coming on May 8 in 1856.

A nonprofit conservation group in Excelsior, the Freshwater Society, made its declaration of ice-out this year at 5:14 a.m. Thursday.