Most people in north central Wisconsin know how to test frozen lakes and ponds for thickness.
"You can take an auger," says ice-fishing guide Justin Gaiche, "You can drill a hole and you can see that you have plenty of ice to support a vehicle, snowmobile or a person."
Gaiche says ice should be clear when it's drilled. Veteran ice fishers to stay away from dark ice that is most likely very thin.
Long-time fisherman Todd Warner and his friend Dave Johnson have been fishing together for about 40 years, but even with decades of experience Warner says neither would venture out onto unfamiliar territory.
"If I was going to go on a lake where I didn't know it," Warner says, "I'd find somebody that did know it."
This is because ice may be safe in one place, but unsafe just a few feet away. This is especially true in places where natural springs feed a lake.
People who do not have a lot of experiencing judging ice are advised to stay away from rivers. The running currents in rivers can make ice very unstable in areas. In general, experts say ice needs to be three inches deep to walk across, five inches deep to snowmobile on and 12 inches deep to drive across.