The subzero temperatures that give Minnesota its frosty reputation blew into the state Friday morning, sending a shiver through some weekend activities and putting others on ice.

And the worst of this winter so far was said to be still on its way next week.

In the Twin Cities on Friday, temperatures hovering around zero left an impression. Extra dogs streamed into a downtown day care, frostbite cases ticked up at a hospital and some events were called off. Gov. Tim Walz even speculated about possibly closing schools next week to protect against the big chill.

But many signature winter events, like the St. Paul Winter Carnival and the U.S. Pond Hockey Championships in south Minneapolis, were still on track to continue through the weekend.

"It's Minnesota — when has the cold hurt you?" said Brittany Schneider while watching the pond hockey activities with her family at Lake Nokomis.

More than 30 Boy Scouts planned to sleep outdoors in DIY shelters this weekend at a camp north of Brainerd. Enduring a night of subzero temperatures will earn them a Zero Hero badge, though organizers said they will be at the ready if the Scouts want to go inside.

"We tell them, 'It is not a shame to say I'm cold,' " said Mary Herlich, camp program manager. "There will be plenty of opportunities to get that Zero Hero badge."

For others, such activities weren't worth the risk.

A group of more than 30 cadets with the Minnesota division of the Civil Air Patrol — most of them teenagers — had planned to spend the weekend in the woods north of Bemidji learning winter survival skills. But the annual training, which includes building shelters and learning how to signal airplanes, was postponed.

"With the cold and the wind temperatures, anytime you're looking at 10 below, 15 below, there's no sense going," said Jim Jagow, chief of staff for the Minnesota Wing Commander of the Civil Air Patrol.

HCMC in downtown Minneapolis had seen six cases of frostbite since Thursday, two of them severe enough to require admission. That brought the overall number of cases this month to 28.

And that could rise even higher next week, when temperatures are forecast to dip deep below zero. Joe Calderone, a senior forecaster with the National Weather Service in Chanhassen, said there will be low double-digit highs on Saturday before the mercury plunges into the negative 20s on Tuesday night following a period of snow.

"We're looking at exceptionally cold air coming in here for the Tuesday-through-Thursday period of next week," Calderone said.

Walz said Friday that his staff was mulling the circumstances under which the state might shut down all schools, as happened in 2014 when temperatures were forecast to drop to 25 to 35 below across the state.

"I've asked my team to put together … the criteria," Walz said. "But in full disclosure, I really trust local officials and superintendents to make these decisions. We'll see when it's the proper role."

In preparation for next week, downtown Minneapolis nonprofit YouthLink — which works with homeless youth — said it would be open 24 hours a day Monday through Friday.

Many people interviewed outdoors on Friday emphasized one word: layers.

"I just think you should dress for it. Don't try to be cute. Layers, layers, layers," said Heidi Iverson, a letter carrier filling up her car at a south Minneapolis gas station.

The number of dogs coming into Downtown Dogs day care goes up by about 50 percent when the weather turns this cold, owner Ralph Bernstein said.

"A lot of it really is about making sure that the dogs get the exercise and runaround and play time that they wouldn't otherwise get because it's just too cold," Bernstein said. "It's unhealthy, even for a dog who lives with a fur coat."

Nick Magrino had planned to host an annual ice-fishing party Saturday with friends on Bde Maka Ska, formerly Lake Calhoun. His family even flew in from Virginia for the event. But he postponed it for the first time in its seven-year existence after closely watching the weather forecast.

"Obviously it's great to embrace winter, but it's not super fun if it's, like, five degrees and cloudy and windy," Magrino said.

Light-rail passenger Brittany Whiteman, enduring her first Minnesota winter, wondered aloud why she had moved here. But she quickly remembered that the summers make it worthwhile.

"I'm glad we live here," she said. "But dang, it's cold."

Staff writer J. Patrick Coolican and University of Minnesota student David Mullen contributed to this report.