A heat wave, of sorts, hit here one day last week. The temperature got up to 5 degrees.

At the Head of the Lakes Resort, Dennis Grythe wore his coat unbuttoned. "Today is nice," he said Wednesday as he stood outside, surveying snow-covered Lake Osakis. "We have to figure it's about 90 degrees warmer than it was over the weekend."

Snow and cold weather are brutal facts of life here where the Minnesota prairie meets the lake country. Sub-zero temperatures are the rule, not the exception, this time of year.

Even when the thermometer dipped to 35 degrees below zero and a harsh wind drove the wind-chill-factored temperature down to 90 below a week ago, Grythe and his partner didn't close the resort bar until 11 p.m.

Some fishermen simply kept fishing through what the radio stations called the coldest day of the century.

"There's something about this part of the country. The worse the weather gets, the more people come out," Grythe said. "It's a challenge."

The wind-chill temperature remained under 40 below for more than 48 hours. But nothing particularly out of the ordinary happened here beyond a few frozen pipes and stalled cars.

There were no fires, injuries or serious frostbite cases reported. Sunday mass at the Church of the Immaculate Conception went off on schedule. Public schools opened two hours late Monday, but they opened, and the Osakis Silver Streaks girls' basketball team played a game that night.

It isn't that the Scandinavians and Germans who settled here are especially hardy people. "People are just people. They put up with what they have to put up with," said Grythe's partner, Wayne Doehling, who moved here last year from "down south" in "the cities," as Minneapolis and St. Paul--120 miles away--are called here.

Winters have always been hard and long here. They usually begin in early November, with the first cold snap, and don't officially end until the ice on the lake breaks up in late April.

When the snow falls, it stays. Seldom does a "heat wave" send the mercury up to thawing temperature, 32, until late February or early March. Days, sometimes weeks, pass without the temperature rising above zero.

There was a time, 40 or 50 years ago, when snowstorms left some farms isolated from the outside world for three or four days. Mail wouldn't reach some for two weeks. Some farmers' wives developed severe cases of depression.

Those days are over.

The winters are as cold as ever. They still produce the usual rounds of colds and flu among the young and heart and lung problems among the elderly. Almost every year someone in the area dies of a heart attack shoveling snow.

But the rotary snowplow, snowmobile and cross-country skiing have revolutionized life in northern Minnesota.

Children wear goose-down jackets and "moon boots" (felt-lined rubber, modeled after those worn by astronauts). Their parents plug electric cords into "headbolt heaters" to start their cars.

"I used to dread winter. Now I can hardly wait until the first snow," said Roger (Rocket) Neumann, who operates a dairy farm and snowmobile outlet here. "My whole outlook on winter has changed."

People use snowmobiles to get to their fish houses far out on the frozen lake, sometimes even to get to work.

There are snowmobile races and "poker runs," a form of bar-hopping where groups of snowmobilers travel from tavern to tavern across the countryside and are given one playing card toward a poker hand at each stop.

Osakis, a resort and dairy farm area in the middle of Minnesota, has 1,306 people, and doesn't have a library or a street light.

There used to be three pool halls, but now there is one, and many old-timers complain that "it's been taken over by TV video games," which makes serious pool-playing impossible.

When I was a boy here, winter almost always found a six-foot drift in our front yard. Banks created by plows along the streets often towered five feet above car tops. One year the snow drifted as high as the roof on our back porch.

Kids looked forward to winter.

We loved and hated the cold. It would eat into our faces, numb our fingers and toes and leave icicles on our eyebrows. But we would stay out for hours. We would ice skate on Mud Lake, and toboggan down Killer Hill, which has now become part of a golf course.

It has been 10 years since I was here in the winter. The snow is 18 inches deep. No one lives in our big old house on Lake Street in the winter any more, and one gets an eerie, snowbound feeling looking out the front window across Lake Osakis, which stretches for 10 miles to the north.

There are about 500 fish houses on the lake this winter. Small, box-like buildings, ranging from 5 by 5 feet to 12 by 20, they have holes in the floor so fishermen can drill through the ice and drop lines into the water.

"The ice gets three or four feet deep by the end of winter," said Mike Mathews, a local insurance man. "The average fish house is carpeted, insulated and paneled. It has a stove and electric lights. The more elaborate ones have television sets and bunk beds. People pull three or four of them together and party all night."

People here work hard, but they aren't obsessed with it. When someone returns here after years of absence, he is asked, "Where you at now?" never, "What do you do?"

When a reporter from The Minneapolis Tribune dropped by a month ago he asked Dr. E. E. Emerson, widely regarded as the smartest man in town, how he spent his time.

Emerson said he didn't do much of anything "except unnecessary things. It doesn't matter that way then if they don't get done."

For some here, work is simply something you do to earn enough money to fish and hunt. What is important here is sports.

Hardly a day goes by when Carl C. Aaberg, 70, doesn't hunt, fish or golf. He keeps two fish houses on the lake, 10 yards apart. One is for himself, the other for his wife.

"I can't stand her in the same fish house. We fight all the time. I try to tell her when to pull in her line, and when to let it run," he said.

"It's a lot harder fishing together than living together."