Twin Lakes saw a lot of action last weekend - but those in charge of the ponds and lakes skaters love to frequent this time of year are still urging caution.
Marc Matsil, Parks and Recreation director for the city, estimates there were 100 skaters on Sunday alone.
"It was pretty incredible," he said. "There were two hockey games going on and three dozen other people (skating). It was pretty packed."
Matsil said skaters should remember to "skate at your own risk and skate with a buddy."
Marc Scholten, whom fellow hockey player Steve Box jokingly calls "the guru of the ice," has been measuring ice thickness to help determine whether it's safe for the last 10 years.
When it's thin, he uses a hockey stick to fracture it, and then looks at the depth of the fracture. When it's deeper, he drills down and uses a tape measure to determine the depth of the hole.
But it's not just about the thickness of the ice, he said - it's also about the kind.
"There are different types of ice just like there are different types of snow, and they all have different structures," he said.
Black ice, which contains no air, is the strongest. Then there's ice that has refrozen, or frozen slush, with air bubbles that weaken the ice.
"So when you're drilling and measuring you want to look at the structure to tell you how strong it is," he said.
Monday morning when he drilled at South Twin Lake, it was 4 ¾ inches; he estimates it's around 8 inches at Mendenhall Lake, where it gets colder.
The Minnesota Department of Natural Resources says 4 inches is a safe depth for ice fishing, skating, or other "on foot" activities on new, clear ice.
The city and the Forest Service do not measure ice depth.
Kevin Brady, parks and landscape superintendent for the city, said the city has ice rescue ladders at five different locations, just in case, though he doesn't know of a case in which someone has had to be rescued. "We don't recommend people skate on it or be on it," he said. "Any kind of unknown depth is risky at best."
Julie Speegle, assistant public affairs officer on the Tongass for the Forest Service, said the agency also abides by the "skate at your own risk" philosophy.
"Our general guidance is (Mendenhall Lake) is never safe to go out on," she said. "Even in the cold of winter the glacier can calve, and if the glacier calves it can send an instant shatter effect through all the ice on the lake."
Speegle said that's happened before, but not for many years.
Ice skater Kathy Callahan has her own rule of thumb for safety - 50 people. She first skated this year early last week, after seeing people playing a hockey game.
She also said you can see the depth of the ice in the cracks.
"The ice is great," she said. "It's not as smooth or flat as indoors, but the scenery is much better."
"The ice is really smooth," said Steve Box, who went out playing hockey with a bunch of other "die-hard pond hockey guys" Monday through Thursday last week. "There's just a light skim of snow on it, and South Twin Lake has blown a lot of that off."
Box's two kids, ages 9 and 10, have also been skating and playing hockey out at Twin Lakes.
"They love playing pond hockey," he said. "You can be there for hours and you don't have to pay or leave in 45 minutes."
This winter, Scholten, Box and the other hockey players will be playing hockey "every noon we've got ice to skate on, wherever the ice is good," Scholten said. "Right now Twin Lakes has got the smoothest ice in town."