WEATHER PREPAREDNESS

Safe Ice Thickness | When Is Ice Safe?

When is ice safe? There is no for-certain absolute answer. Really, ice should never be considered safe. Though there are some ice thickness safety guidelines to follow (listed below).

Ice Safety

You can’t judge the strength of ice just by its appearance, age, thickness, temperature, or whether or not the ice is covered with snow.

Ice strength is based on ALL these factors — plus the depth of water under the ice, size of the water body, water chemistry and currents, the distribution of the load on the ice, and local climatic conditions.

New Ice vs Old Ice

New ice is usually stronger than old ice. Four inches of clear, newly‑formed ice may be a safe ice thickness support one person on foot, while a foot or more of old, partially‑thawed ice may not.

Ice Thickness Uniformity

Ice seldom freezes uniformly. It may be a foot thick in one location and only an inch or two just a few feet away.

Ice Over Flowing Water

Ice formed over flowing water and currents is often dangerous. This is especially true near streams, bridges and culverts. Also, the ice on outside river bends is usually weaker due to the undermining effects of the faster current.

Snow Over Ice

The insulating effect of snow slows down the freezing process. The extra weight also reduces how much weight the ice sheet can support.

Ice Near Shore vs Farther Out

Ice near shore can be weaker than ice that is farther out.

Booming Ice

Booming and cracking ice isn’t necessarily dangerous. It only means that the ice is expanding and contracting as the temperature changes.

Fish Movements

Schools of fish in a given location can also adversely affect the relative safety of ice. The movement of fish can bring warm water up from the bottom of the lake. In the past, this has opened holes in the ice causing snowmobiles and cars to break through.

Safe Ice Thickness | Guidelines

For New, Clear Ice Only (and listed caveats)

2″ Ice or less – STAY OFF!

4″ Okay for Ice Fishing or activities on foot

5″ Ice Thickness for Snowmobile or ATV

8″ – 12″ Thick Ice for Car or small Pickup

12″ – 15″ Ice Thickness for Medium Truck

How To Check Ice Thickness

One way is to use a cordless drill with a Long 5/8 inch Wood Auger Bit (like this one on amzn). It won’t take long to drill through the ice to check the depth. Just use a small tape measure to check.

White Ice vs Clear Ice

White ice, sometimes called “snow ice,” is only about one-half as strong as new clear ice so the above thicknesses should be doubled.

Ice Thickness Can Vary Widely

Ice is seldom the same thickness over a single body of water. It can be two feet thick in one place and one inch thick a few yards away due to currents, springs, rotting vegetation or school of rough fish.

Vehicle Spacing On Ice

Vehicles weighing about one ton such as cars, pickups or SUVs should be parked at least 50 feet apart and moved every two hours to prevent sinking. It’s not a bad idea to make a hole next to the car. If water starts to overflow the top of the hole, the ice is sinking and it’s time to move the vehicle!

Never Go Out Alone

Use the Buddy System. Have a length of rope. If you go through the ice while you’re alone, well, that’s bad on you.

The Most Popular Ice Cleats

Crampons Ice Cleats
(view on amzn)

Some ice safety data sourced from the Minnesota Department of Natural Resources – I figured that those in MN certainly ought to have good information about this! (“Land of 10,000 Lakes”)

Continue reading: Wind Chill Frostbite Chart

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14 Comments

  1. When I used to ice fish for salmon in the High Rockies, I made a pair of short ice picks, one for each hand, and had them fastned by a loop to each wrist. That way if I did go through the ice, I had a pick right there for each hand, and I could pull myself out. Simple as a sharpened 1/4″ spike in a chunk of broom handle with a paracord loop. Never had to use them, but still would not go out on ice without them.

  2. Personally I don’t even like going out on that 1/4 inch of ice on my driveway, all alone over a Lake/Stream/River….. No Thanks.
    AND no way in heck I’m going out on Navajo Lake when it freezes, at more than 400 foot deep in places it takes about 25 seconds for the body to shut down when submersed in freezing water.
    But thanks for the Article Ken, good info as usual.

    1. But you could cut the ice in blocks and pull it up, maybe retrieve some of the artifacts left by previous boaters…

  3. How safe is it? How fast can you drive a snowmobile or 4 wheeler across it?
    I grew up in the Adirondack Mtns. 1 time I went across the river in town and I probably shouldn’t have. I had a 110 Honda 3 wheeler. I started to break through. I stepped on it and made it across. I didn’t go back home that way.
    There are too many stories about people falling through, losing a car or a shack. 1 family went out (4 kids Mom and Dad) and fell through. Only the dad and 1 son came back. The next year the dad and son didn’t come back.
    No thank you.

  4. Another thing to watch for if you decide to go out onto ice in a reservoir, and that is falling water level. Here in the West, reservoirs draw down water for domestic use all the time. I once saw a small inlet covered in ice, but on the main part of the reservoir the ice appeared to be lower. I quickly realized that the inlet ice was hung up above the water level several feet. That could have been really bad, go through the ice and fall a couple of feet to the water below, you’d never get out! These days the closest I want to get to dealing with ice is for the cool chest, or maybe in a tumbler of “organic solvent” for the holidays.

  5. As a teenager i saw a large chunk of ice on on of Michigan’s great lakes break off, ice fisherman would fish close to the edge and open water. The Coast Guard chopperpick about 5 people and gear off the ice flow which was about 30 foot across. Never will forget the look on the people’s faces floating away on the ice flow, wave action broke the chunk off.

    I’ve travelled way out to a rented spear fishing shanty in an old station wagon with the top cut off, Lake St. Clair-Michigan again, if we went in water due to an open pocket or weak ice, the theory was you could get out of the vehicle, only did it once, which was enough due to the “excitement factor” (fear factor) and cold doing 40-50 miles per hour.

    There is an old study by the Navy, I recall correctly, measuring harmonic wave action of thick ice due to vehicles travelling on it. Two frogmen (can i still say frogMEN, or should i say underwater-breathing assisted biped humanoids?, I’m so confused…🤤), in a car purposely went through the ice for research on what happens, reading what happens stopped me from ever going on the ice except by foot. ice harmonics are very bad thing.

  6. There are many precautions to take when out on the ice.
    #1 Wear a life jacket.( They snicker at me all the time) but screw them.
    #2 Ice forms from the shore outward. As you start out use a spud bar every 20ft. to make a hole and check the thickness.
    #3 Carry a boat seat cushion with 25-30 ft. of rope attached that you can
    throw to any knuckle head that goes for a swim.
    #4 Never walk shoulder to shoulder with your pals.20 ft. apart is about right. One person thru the ice is enough.
    #5 Carry an emergency whistle on a lanyard around your neck.If it’s windy
    yelling for help is not much good. Three blasts on the whistle should get some attention.
    #5 If you go out on an ATV over inflate the tires to 8-10 lbs. It will keep you afloat a few minutes. Emphasis on “a few”.
    #6 When in doubt stay in the truck with coffee and Blackberry Brandy!

  7. Kula,
    Ok, rub it in. Now you are doomed. I can see the Honolulu Times Christmas edition headline now: “Rare ice storm blankets the Islands with 2″ of ice”.
    Happy Holidays!

  8. Went through the ice beaver trapping years ago. Temperature was in the teens, made it about 100 yards and pants froze up. Had to remove them and keep moving to finally make it to my trapping partners’ jeep. That was a long cold ride home. Ice was a good 7″ thick on most of the lake. I found a spot that day that wasn’t.

  9. When you leave to go ice fishing in the morning and wifey tells to be home by 5pm. sharp for supper just say “yes dear”.
    Then stop off for a couple brews and straggle in around 8pm.
    She will be glad you are alive and not mad anymore.
    Well maybe.Probably not.
    Safer to just do as we are told.

  10. When I was young I would sometimes go through a small swampy area when going to a friends house. Walking across the frozen swampy area was nice as it was quicker. The water wasn’t deep (6″ to 12″) but had several feet of black thick muck below that. Foot went through a few times over the years and realized one thing (yeah, it took me a while-thick headed and all) that places with vegetation sticking through the ice (such as cattails) the ice was thinner and/or weaker in those locations.
    Just something I noticed.

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