My one caution would be just make sure you check with locals before you actually head out on the ice! Last year a few of the lakes I fish in northern WI were awfully late ice up, we could walk out on two-three inches only by the 2nd or third week (around the 12-15)of December. Guys not familiar with the lakes freezing dynamics earlier in the season looked at the calendar and just assumed by X-mas time the ice was good enough to drive on, as a result many vehicles went through. So just double check before heading out. I would say for central/north-central WI lakes second to third week is a safe bet that you can find good ice somewhere.