The Portage Lake Lift Bridge reflects in the ice and water on the Portage Canal Friday afternoon. The Hancock Police Department posted a warning on social media after conducting a rescue of a number of people who had fallen through thin ice on Thursday. (Mark Wilcox/Daily Mining Gazette)

The Bootjack Fire Department is cautioning the public to stay off the ice on Torch Lake, due to unseasonably warm weather and thin ice.

Fire Chief Dan Sarazin that in many places, the ice is two inches in thickness or less, and in areas where currents flow beneath the ice, the ice is still more unstable.

Sarazin said that his department on Thursday used its air boat to reach a party of skaters and warn them of the hazard.

“They were young skaters,” he said, “and when we advised them on the ice conditions, they said they would skate on Portage Lake. That’s even worse.”

Sarazin is not wrong. On Thursday at 10 p.m. the Hancock Police Department issues a similar warning on social media, warning people to stay off the ice:

“That’s it, if there is ice, especially on Portage lake or anywhere near the lift bridge.,” the warning states. “Stay off it, especially in these temperatures. IT IS DANGEROUS.

Even though we have a search and rescue team that can do ice rescues, we would rather avoid putting them and you in that situation.”

The DNR does not recommend the standard “inch-thickness” guide used by many anglers and snowmobilers to determine ice safety. A minimum of four inches of clear ice is required to support an average person’s weight on the ice, but since ice seldom forms at a uniform rate it is important to check ice thickness with a spud and ruler every few steps.

MSU Extension offers these tips on what to know about ice:

You can’t always tell the strength of ice simply by its look, its thickness, the temperature or whether or not it is covered with snow.

• Clear ice that has a bluish tint is the strongest. Ice formed by melted and refrozen snow appears milky, and is very porous and weak.

• Ice covered by snow always should be presumed unsafe. Snow acts like an insulating blanket and slows the freezing process. Ice under the snow will be thinner and weaker. A snowfall also can warm up and melt existing ice.

• If there is slush on the ice, stay off. Slush ice is only about half as strong as clear ice and indicates the ice is no longer freezing from the bottom.

• Be especially cautious in areas where air temperatures have fluctuated. A warm spell may take several days to weaken the ice; however, when temperatures vary widely, causing the ice to thaw during the day and refreeze at night, the result is a weak, “spongy” or honeycombed ice that is unsafe.