Ice Safety and Ice Thickness

No ice is safe ice

That’s the Wisconsin DNR’s message every winter ¹. Temperature swings, wind, currents, and springs vary across the state and across a single lake; ice can be 2 ft thick in one spot and an inch thick a few yards away ². Neither the Wisconsin nor the Minnesota DNR measures or monitors lake ice; the responsibility is yours ^{1 2}. For current conditions, ask local fishing clubs, bait shops, and outfitters, who check it routinely ¹.

Thickness guidelines

The Minnesota DNR’s guidelines are for new, clear ice ²:

White ice, formed when snow melts and refreezes, is only about half as strong as clear ice, so double the figures ². Thickness isn’t everything: temperature, snow cover, currents, and decaying plants all weaken ice ². A UTV weighs roughly 3,000 lb, about the same as a car ¹. Move parked vehicles every two hours and keep them at least 50 ft apart ².

Where ice is thin

• Inlets, outlets, and narrows where current flows under the ice.
• Springs, which keep water moving and warmer.
• Pressure ridges and heaves, cracks pushed up by expanding ice, are signs of thin spots ¹.
• Around docks, reeds, logs, and rocks, which absorb sun.
• Dark, gray, or slushy patches, and ice under deep snow, which insulates it from freezing.
• Early and late season, especially after a warm spell.

Test as you go

Carry a spud bar (an ice chisel) and strike the ice ahead of you as you walk to new areas ¹. If it goes through in one or two hard blows, turn back. Drill test holes with an auger and measure. Travel with a partner spread apart, avoid unfamiliar areas, and stay off the ice at night ¹.

What to carry

The Wisconsin DNR’s list ¹:

• Hand spikes (ice picks) around your neck or in a top pocket, and a length of light rope.
• A life jacket or float coat for everyone.
• Creepers on your boots for traction.
• Extra mittens and a charged phone.
• Tell someone where you’re going and when you’ll be back.

If you go through

The first danger isn’t hypothermia; it’s cold shock. Sudden immersion makes you gasp and hyperventilate, and cold shock can kill within seconds to two minutes ³. Then your arms and legs weaken progressively: in water near 32 °F, a person can be incapacitated within 2-10 minutes ³. That’s why the popular “1-10-1” rule is misleading: you don’t get a guaranteed minute, ten minutes, and an hour ³. A float coat or life jacket keeps your head up through the gasping, and thermal protection buys time ³.

1. Keep your head up and get your breathing under control.
2. Turn back toward the way you came: that ice held you.
3. Arms out on the ice, kick your legs up behind you, and pull with your ice picks.
4. Roll away from the hole to spread your weight, then crawl back along your track.
5. Get warm and dry immediately and call for help ¹.

Helping someone else: don’t run to the hole. Call 911, then reach with a rope, pole, or branch from solid ice, lying flat; rescuers should also be tied to a rope ¹.

Try it

Before the season, make or buy ice picks and wear them on every trip. On your first outing of the winter, go with someone who knows the lake, carry a spud bar, and drill and measure five test holes as you go.

What to take from this

No ice is safe ice, and the DNRs don’t check it. For clear ice, 4 in. is the minimum for walking and 5-7 in. for a snowmobile; double for white ice, and avoid inlets, outlets, springs, pressure ridges, and dark patches. Test with a spud bar, carry ice picks, rope, and a float coat, and tell someone your plan. If you go through, cold shock is the first danger: keep your head up, breathe, turn back the way you came, kick and pull out, roll away, and get warm.