Burt King reports that the ice 20 feet off his shore is between eight and nine inches thick. However, exercise caution when out on the ice, as there are several springs that create thin ice.
Burt also provided some helpful links from the DNR, available below. Please remember to be very cautious.
http://www.dnr.state.mn.us/safety/ice/thickness.html
http://dnr.wi.gov/topic/outdoorrecreation/activities/icesafety.html