
- the quality of ice
- its thickness
- ice and air temperatures, and
- solar radiation
Appearance
Strongest Ice | Clear blue or blue-black and FREE of snow, air bubbles and debris |
Weak Ice | White, brittle, mixed with snow or filled with air bubbles |
Suspect Ice | Gray indicating presence of water as a result of thawing - cannot bear loads. |
New ice is usually stronger than old ice as bonds between the crystals decay with age, making the ice weaker even if melting has not occurred.
Thickness
Rivers | Lakes |
Maximum every 50 feet (15 meters) | Maximum every 100 feet (30 meters) |
Thickness Guide
Less than 3 inches (7.5 cm) | Avoid, it can break any time under the weight of an average person |
3 to 5 inches (7.5 - 13 cm) | Capable of holding a person; groups should spread out. |
6 to 8 inches (15 - 20 cm) | The minimum needed for group activity |
Stationary Loads and Vehicles on Ice
- the weight and distribution of the load(s) on the ice
- an unintended stationary load on the ice (when a load "sits" or stops on the ice)
- the speed of the vehicle
- other traffic or loads on the ice
- frequency of loads
- continuous use areas (such as ice crossings, parking areas, bridge sites)
- reduced ice thickness close to shoreline
Effective Ice Thickness For Moving Loads
Permissible Load
(clear, blue ice) |
Effective ice thickness | |
Lake | River | |
Passenger Car 2000 kilograms | 7 inches / 18 cm | 8 inches / 21 cm |
Light truck 2500 kilograms | 8 inches / 21 cm | 9 inches / 23 cm |
Medium truck 3500 kilograms | 10 inches / 26 cm | 12 inches / 30 cm |
Heavy truck 7000 to 8000 kilograms | 14 inches / 35 cm | 16 inches / 41 cm |
10,000 kilograms | 15 inches / 38 cm | 17 inches / 44 cm |
25,000 kilograms | 25 inches / 63 cm | 29 inches / 73 cm |
45,000 kilograms | 31 inches / 80 cm | 36 inches / 92 cm |
70,000 kilograms | 39 inches / 100 cm | 45 inches / 115 cm |
110,000 kilograms | 49 inches / 125 cm | 57 inches / 144 cm |
Effective Ice Thickness for Stationary Loads
Permissible Load
(clear, blue ice) |
Effective ice thickness | |
Lake | River | |
1,000 kilograms | 8 inches / 20 cm | 9 inches / 23 cm |
2,000 kilograms | 12 inches / 30 cm | 14 inches / 35 cm |
4,000 kilograms | 18 inches / 45 cm | 20 inches / 52 cm |
8,000 kilograms | 24 inches / 60 cm | 27 inches / 69 cm |
25,000 kilograms | 43 inches / 110 cm | 50 inches / 127 cm |
45,000 kilograms | 59 inches / 150 cm | 68 inches / 173 cm |
70,000 kilograms | 71 inches / 180 cm | 82 inches / 207 cm |
110,000 kilograms | 91 inches / 230 cm | 104 inches / 265 cm |
Under thawing temperatures where the average air temperature exceeds 8 degrees Celsius, increase the required ice thickness given in the tables by 20 percent or reduce the allowable weight by one-third.
Temperature Variations
- 5 degrees Celsius or less - multiply the minimum ice thickness by a factor of 1.4
- 5 to 10 degrees Celsius - multiply the minimum ice thickness by a factor of 2.0
- 10 degrees Celsius or more - multiply the minimum ice thickness by a factor of 2.4
Basic Ice Safety Practices
- Never go alone or attempt to rescue a victim of ice failure alone
- stay away from cracks, seams, pressure ridges, slushy areas and darker areas that signify thinner ice
- listen for loud cracks or booms coming from the ice and know what they indicate
- always wear a life jacket or personal flotation devide (PFD) over an ordinary snowmobile suit or layered winter clothing
- Never wear a life jacket when traveling across ice in an enclosed vehicle as it can hamper escape in case of a breakthrough
If you get into trouble and you're by yourself:
- Call for help
- Resist the immediate urge to climb back out where you fell in
- Use air trapped in your clothing to get into a floating position on your stomach
- Reach forward onto the broken ice without pushing down, kick your legs to push your torso onto the ice
- When back on the ice, crawl on your stomach or roll away from the open area with arms and legs spread out as far as possible to distribute body weight
- Do not stand up! Look for shore and make sure you are going in the right direction
When you are with others:
- Rescuing another person from ice can be dangerous, perform the rescue from shore
- Call for help either from trained professionals and bystanders
- Check if you can reach the person using a long pole or branch from shore - if so, lie down and extend the pole to the person
- If you go on ice, wear a PFD and carry a long pole or branch to test the ice in front of you whil carrying something to throw to the person
- When near the break, lie down to distribute weight and slowly crawl to the hole
- Remaining low, extend or throw your emergency rescue device to the person
- Have the person kick while pulling them out, then move the person to a safe position on shore or where you are sure the ice is thick