Julie Opdahl doesn't need a thermometer to know that it's cold outside.

"My cats won't go outside when it's below zero," said Opdahl, who runs a used car lot and service station with her husband in Litchville, in central North Dakota.

The Opdahls, like most North Dakotans, have adapted to cold. And while they may complain a little, most take it in stride.

"It's only 31 below," said Randy Hjelmstad, owner of Randy's Refuse in Grand Forks. "It's not that bad out."

It was bad enough that Xcel Energy asked its Upper Midwest customers in North Dakota, Minnesota, Michigan, South Dakota and Wisconsin to conserve electricity over the next few days to reduce strain on the power grid. The company said it has enough electricity supplies "but it is possible that electricity reserves could tighten as people begin to use more during evening hours."

Montana-Dakota Utilities, based in Bismarck, said it did not have similar constraints, though it had been alerted by a Midwest transmission monitoring agency that supplies could be tight.

"For North Dakota, it's not business as usual, but it's not anywhere near as critical as it is in Minnesota," MDU spokesman Dan Sharp said. "If it does anything, it emphasizes the continuing need for utilities like ours to plan for additional generation and new construction."

While her cats stayed warm inside on Monday, Opdahl and her husband, Gary, had to work outside, jump-starting cars in 11-below-zero temperatures.

"We've got frozen, dead batteries to the max," Opdahl said. "It's a pain."

Grand Forks temperatures dipped to 31 below zero early Monday morning at the city's airport, which was 3 degrees colder than the record set in the years 1982 and 1967, the National Weather Service said.

"It was a relatively mild record low," said Bill Barrett, a weather service meteorologist in Grand Forks.

The official temperature, taken within the city, was 27 below on Monday, far from the city's record low of 41 below set in 1936.

"That one is still intact," Barrett said.

"It's cold but not record cold," said Bill Abeling, at the National Weather Service office in Bismarck. "To get record temperatures this time of year in North Dakota, you've got to delve down in the 40-below region, so we're not even close."

Winds were mostly calm across the state Monday, sparing residents from even more bitter temperatures, Abeling said.

Hjelmstad, the Grand Forks garbage disposal operator, said he hears people "whine about the weather" sometimes. But he said the old-timers had it worse, especially in his profession. With automation, he said, "you don't even have to get out of the truck anymore."

Alida Wiest, who works at the Weigel Funeral Home in Mandan, said cold weather no longer stops burials due to frozen ground.

"It used to be that way, where they'd hold a body until spring. But now there are backhoes and earthmovers," she said.

"We do burials year round now," Wiest said. "I've never seen cold weather stop a burial yet."

A bone-chilling cold wave with temperatures as low as 42 below zero shut down schools for thousands of youngsters Monday, sent homeless people into shelters and put car batteries on the disabled list from the northern Plains across the Great Lakes. At least four deaths were linked to the cold weather.

The cold was accompanied by snow that was measured in feet in parts of upstate New York.

"Anybody in their right mind wouldn't want to be out in weather like this," Lawrence Wiley, 57, said at Cincinnati's crowded Drop Inn Center homeless shelter, where he has been living. Monday lows were in the single digits.

With temperatures near zero and a wind chill of 25 below, school districts across Ohio canceled classes. "We have a lot of kids that walk to school. We didn't think it was worth the risk," said Sandusky City Schools Superintendent Bill Pahl.

It was so cold that Toledo, Ohio - 5 above zero at noon, up from 4 below - even closed its outdoor ice rink. "The irony is not lost on us," said city spokesman Brian Schwartz.

With a temperature of 12 below zero and wind chill of 31 below, Wisconsin's largest school district, Milwaukee Public Schools, also shut down, idling some 90,000 children. In upstate New York, 34,000 kids got the day off in Rochester because of temperatures near zero. Schools also closed in parts of Michigan and Illinois. A few schools closed even in Minnesota, where February cold is the norm and people are accustomed to coping.

Temperatures dropped below zero in Minnesota on Saturday morning and were expected to remain there until sometime today, the weather service said. Subzero temperatures blanketed the Minneapolis-St. Paul area for 63 straight hours - the longest stretch since 2004 - ending Monday afternoon.

In northern Minnesota, the temperature crashed to 42 below Monday morning at Embarrass, 38 below at Hallock and 30 below at International Falls, the weather service said.