Chicago: Just before the dangerously cold temperatures set in across the Midwest this week, Michael Belz was occupied with thoughts of his son Gerald, an 18-year-old in his first year at the University of Iowa.

Classes at the university had been cancelled. Campus was only a half-hour away from the Belz home in Cedar Rapids. But Gerald had opted to stay put and wait out the cold snap in his dorm.

“At the time, I thought that was the smart move,” Michael Belz said, remembering that his son had trouble getting his truck started the weekend before. “I didn’t want him to get stuck somewhere driving. So he decided he would stay.”

Early on Wednesday morning, as the temperatures were plummeting, Gerald Belz was found unconscious outside a campus building, a short walk from his dorm. He died later at a hospital. Investigators believe his death was related to the sub-zero temperatures that plunged Iowa and all of the Midwest into a miserable and dangerous cold snap this week.

He is one of at least 21 people whose deaths, government officials say, are believed to be related to the bitter weather system that has paralysed the region. The frigid conditions have sent scores of people to hospitals with symptoms of hypothermia or frostbite, and have closed businesses, schools and many colleges.

Many of the deaths, which occurred since Sunday, were still being investigated, and precise causes had not yet been established. But officials said in each case that they believed the weather had played a role.

Among those who have perished, according to local coroners, police and fire departments and other officials: Four men found frozen near their homes in Illinois, Wisconsin and Michigan; six people who died in traffic crashes in Iowa; a pedestrian hit by a snowplough in Libertyville, Illinois; a man found dead between two FedEx trucks at a distribution centre in East Moline, Illinois; and a woman found frozen to death inside a Milwaukee apartment after the thermostat malfunctioned.

Since the polar air mass set in, several cities have hit record low temperatures, and it appeared that Illinois may have broken the state’s all-time low: A weather observer in Mount Carroll, Illinois, recorded a temperature of minus 38 degrees Celsius on Thursday morning.