An arctic blast that has much of the nation in an icy grip is taking a toll on Minnesotans, sending dozens to hospitals with severe frostbite, bursting water pipes and flooding homes, sidelining cars with dead batteries and flat tires and backing up ore boat traffic on Lake Superior.

The deep-freeze free-fall that began Christmas Day made the final week of 2017 in the Twin Cities the coldest in 132 years with an average temperature of 3 below. Relief is on the way, but slowly, with Thursday and Friday’s high temperatures staying in the single digits, moving into the teens on Saturday and hitting near normal — in the mid-20s — by Sunday.

Despite the stretch of biting cold temperatures, the winter season, at least so far, has been deemed mild by those who track the so-called Winter Misery Index.

With little snow and only eight days at 0 degrees or colder, the Misery Index has racked up only 17 points tallied when snow and temperatures fall.

“That’s pretty wimpy,” said Pete Boulay, climatologist with the Minnesota Department of Natural Resources.

For those who remember the bitter polar vortex season in 2013-14, 50 nights at 0 degrees or colder helped pushed the misery index to 207 points. Still, this season’s dangerously cold temperatures are causing plenty of misery for some.

Regions Hospital in St. Paul has treated more than 25 cases of frostbite since Christmas Eve, including 15 patients who were admitted to the hospital. In Minneapolis, Hennepin County Medical Center has treated 26 cases, including 14 admissions. Doctors eyeing the forecast expect those numbers to rise.

The homeless population often is at risk for exposure during cold snaps but most of the recent cases have involved others not dressed for the extreme cold.

“The colder it gets, the more rapidly frostbite can happen,” said Dr. William Mohr at Regions Hospital. Add wind or wet conditions and frostbite sets in even quicker, Mohr added. “We’ve had people who run outside on New Year’s Eve to try to keep their intoxicated friend from driving,” he said. “That’s a hero. But in this weather, it can have consequences … in just 15 minutes of being outside.”

Some of the frostbite cases include those who were stranded in a disabled car, a fall outside that left someone helpless, a person locked out of their house, an outdoor athlete who ignored the symptoms of frostbite.

“These are all circumstances that all of us can imagine being in,” Mohr said. “These could be anybody.”

During a mild winter, Mohr said Regions might treat five to 10 frostbite cases. The year of the polar vortex, the hospital treated 55 to 60 cases, he said.

Most Minnesotans who are over 10 years of age probably have experienced “frostnip” — a superficial frostbite on their nose, ears, toes and fingers with little or no damage, Mohr said. If the skin turns white and numb, go indoors and warm up, he said. If the color doesn’t return and numbness continues after 15 minutes, get medical help.

Severe frostbite can cause long-term damage. At minimum, areas that suffer frostbite could become more sensitive to the cold and prone to frostbite. In severe cases, digits and limbs may have to be amputated. Cartilage that’s been damaged is more susceptible to arthritis.

Broken pipes, dead cars

The cold also is taking its toll on some businesses and homes where sprinklers or water pipes have frozen and burst.

David Gates, general manager at Lindstrom Restoration in Plymouth, said his company responded to a dozen calls on Tuesday as temperatures rose into the teens.

“The water in the pipes freeze, the pipes expand and weaken,” Gates said. When temperatures warm, the pipes burst. He expects another flood of calls when the temperatures rise later this week and when some people, who turned their thermostats down, return from extended trips.

In Duluth, utility crews repaired several water main breaks in one day a couple weeks ago, utility operations supervisor Chris Kleist said. Though the rate of breaks has dropped to about one a day, the jobs to fix them are tougher. With frost about 3 feet deep into the soil, it can take several hours to dig down to the pipes. Hydraulics, diesel engines and other tools don’t work as well in the cold, either.

Subzero temperatures also are slowing the process of loading iron ore onto freighters bound for ports in Duluth-Superior and Two Harbors. Trains bringing the ore to the docks must deal with freezing brakes, conveyor belts at the loading facilities stiffen and iron ore pellets clump up, forcing facilities to separate them with steam, said Adele Yorde, public relations director with the Duluth Seaway Port Authority. The decks of the vessels also get thick ice formed from spraying water, sealing up hatch covers on cargo holds.

Meanwhile, tow truck operators are responding to calls of dead batteries and cold-induced flat tires.

“We’re being slammed with calls,” said Michelle Kretzmann, dispatcher at Bobby and Steve’s Auto World in Minneapolis. “We’ve been busy for the last nine days.”