How can I tell if the lake ice is safe?
—Nicole Green, via e-mail
The only way to be 100 per cent safe around lake ice is to stay off it completely. (Sorry to put a damper on your plans for winter fun.) But that said, the Canadian Red Cross recommends that ice be at least 15 cm thick for a single person walking or skating; 20 cm thick for a group; and 25 cm thick for snowmobiling. You can check ice thickness with an ice auger or an ice chisel; you can also ask for advice from local authorities, your municipality, or your lake association—all may monitor ice thickness on your lake. Ice colour can give you a clue as to its strength: Clear blue ice is the strongest; opaque white ice is about half as strong; and grey ice isn’t strong at all—there’s probably water in the ice, from melting.
Remember that ice thickness varies throughout the winter and on different parts of the lake. It’s affected by all sorts of factors including depth and size of the water body, currents, salt content, snow cover, and, of course, the weather.
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