Bitter cold spreads across the US

Frostbite and hypothermia are real dangers

The Northeast and Midwest US are expected to experience some of their coldest weather in years, as Arctic air makes its way south from Canada.

Schools were closed for the day in Michigan, Iowa, Ohio, Illinois and upstate New York because of the cold.

The National Weather Service said the below-zero temperatures and harsh winds would likely persist into the weekend.

The cold weather is also thought to have contributed to the death of five people and dozens of traffic accidents.

The BBC's Weather Centre forecast a high of -17C (1.4F) in Chicago, Illinois, on Friday, with locals expecting wind chills of -25F to 45F (-31C to -42C).

In Detroit, Michigan, the wind chill was at -35F (-37C).

The US National Weather Service (NWS) said strong, cold winds could lead to hypothermia, frostbite and death.

"When you have these cold temperatures, it doesn't take very long for skin to freeze," NWS meteorologist Rod Donavon said.

Locked out

Five deaths this week have been linked to the severe weather, the Associated Press reported.

In Illinois, a 37-year-old man was found dead on Thursday in the snow outside his home without a coat, hat or gloves.

A 50-year-old man in south-eastern Michigan also appeared to have frozen to death after being locked out of his home overnight.

Earlier in the week, a Wisconsin man froze to death after he apparently went sleepwalking outdoors in bare feet.

In Minnesota, a 77-year-old man was found dead outside his home on Tuesday morning, while a 70-year-old died in a hospital after he was found early on Wednesday.

Frosty weather has also hit Mississippi, Alabama, Georgia and South Carolina.