Ice fishing safety: how thick does ice need to be?

The thickness table everyone starts from

This table only applies to clear ice

That table describes new, clear, solid ice. White, cloudy or snow-formed ice is weaker because air gets trapped in it as it forms, and it can be only half as strong as clear ice of the same thickness. The standard advice is to double the thickness requirement for white ice, meaning the numbers in the table above roughly double before the same activity is considered reasonable.

Ice doesn't form evenly, and you can't judge thickness or strength by looking at it from shore. The only reliable way to know what you're standing on is to measure it yourself at multiple points as you go, not just once near the access point.

A lake can easily have both kinds of ice within the same square mile: a clear, solid sheet in one cove and a weaker, snow-insulated patch a short walk away where drifting snow slowed the freeze. Treat every new area you walk onto as its own test, even on a lake you've fished for years.

Spots that are never as strong as they look

• Pressure ridges, where ice has buckled or cracked and refrozen, are weak points even when the ice around them looks solid.
• Areas near inlets, outlets and springs stay thinner because moving or slightly warmer water underneath slows freezing.
• Ice near docks, bridge pilings and anything metal tends to be thinner because these objects absorb and hold heat.
• Ice changes day to day with temperature, snow cover and wind, so yesterday's safe ice is not a guarantee for today.
• Dark or slushy patches on top of the ice often indicate weaker ice underneath.
• Areas with current, such as near a river mouth or a narrows between two bodies of water, rarely freeze as solidly as a calm, open bay.

Gear worth carrying every trip

• Ice picks, worn around your neck, so you can grip the ice and pull yourself out if you go through.
• A spud bar to test ice ahead of you as you walk, especially early and late in the season.
• A tape measure or auger to actually check thickness once you've opened a hole.
• A rope and a float or flotation device that can be thrown to someone who's gone through.
• A phone in a waterproof case or pouch, kept on you rather than in a sled or bag that could separate from you.
• A whistle, which carries farther than a shout if you need to signal for help across open ice.

How to check as you go

Drill or chip a test hole every so often as you move further out, not just once. Measure from the top of the ice to the waterline underneath, and keep moving to a new area if you notice the thickness dropping or the ice sounding and feeling different underfoot. A sudden crack or a hollow, booming sound is worth stopping and reassessing immediately.

Early-season and late-season ice is the least predictable, since it's either still forming or starting to break down from longer days and warmer temperatures. Many of the most serious ice incidents happen during these transition periods, not the depth of winter.

Walking in a small group rather than alone, and spreading out rather than clustering together, both reduce risk: a group can summon help faster, and spacing out means less total weight concentrated on any one patch of ice.

If someone goes through

Call for help immediately if you have signal. Don't walk or crawl directly to the hole to help someone yourself, since that puts a second person on the same weak ice. Instead, extend a rope, pole, or anything long you have on hand, and try to pull them toward existing solid ice rather than straight up through a widening hole.

If you're the one who goes through, try to stay calm, turn to face the direction you came from since that ice already held your weight, and use ice picks to get a grip and kick to help pull your body horizontally onto the surface rather than trying to climb straight up and out.

Always check your state's guidance

Ice conditions vary enormously by region, lake and even by the specific bay or cove you're fishing. State natural resource and wildlife agencies publish current ice reports and local advisories for popular fishing lakes, and these should always take priority over general rules of thumb. When conditions are reported as questionable or unverified, treat the whole lake as unsafe until you've confirmed otherwise yourself.

Where this matters most

Northern ice-fishing lakes like Lake Mille Lacs, Leech Lake and Lake Vermilion in Minnesota, Lake Winnebago in Wisconsin and Houghton Lake in Michigan all draw heavy ice traffic every winter, and all of them have seen the same hazards described here: pressure ridges, thin spots near inlets, and ice that looks fine but isn't. Checking LakeScope for current water temperature and conditions before a trip is a useful first step, but it's never a substitute for measuring the ice yourself and following your state agency's advisory for that specific lake.

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