What is it like to go to work in a 'polar vortex'?
Temperatures have plummeted across swathes of the US as the so-called "polar vortex" brings arctic air south.
Some schools and businesses have closed and a state of emergency has been declared in a number of US states.
While many people are trying to keep warm at home, we spoke to some of those braving the extreme cold and venturing outside.
- What is a polar vortex?
- Polar vortex in pictures
Brett Thicke is the public works supervisor for the village of Richfield, Wisconsin.
He has been keeping the roads in the rural area clear during the extreme cold weather.
"There's nothing that I can even compare it to," Brett says. "I try to think about the coldest I've ever been, then multiply that by a factor of 10. It is an incomprehensible cold to explain.
"We are near -50F in Richfield today. With the little bit of facial hair that I have, the second you walk outside it feels like each follicle stands straight at attention, even when its fully covered."
"Your eyes start to water from the blistering wind and almost instantaneously it starts to freeze in the corners and on your eye lashes.
"Even with multiple thermal layers, the cold pierces through the work boots.
"Today we could only run the snowploughs for about three hours because the hydraulic fluid in the plough started seizing up due to the frigid temperatures," Brett said. "In all my years, I've never seen this happen before."
Brett says he takes pride in keeping his community safe and providing for his young family, and that helps motivate him while working in the cold.
'Work hard to stay warm'
Jim Garde has been fixing burst water pipes in Madison, Wisconsin, for 16 years.
"The colder it gets, the busier we get," Jim says. "You just have to deal with it."
"It's not the most fun thing to be out in this weather, especially if you're out after dark when it gets even colder. We can get called out at any time, and it won't be nice to be out tonight.
"You have to keep moving or you just get so cold. You have to work hard to stay warm."
One of the main worries Jim has about working outside when the temperature drops is the icy road conditions.
"You hope people keep your safety in mind when they are driving, but you worry about them losing control. The city gives us high visibility jackets."
Jim says the thing that is helping him through this cold snap is the crew he works with.
"You have to try and have a good time in the cold, you need people around you to make you laugh and that there is a light at the end of the tunnel."
While a number of airports in the US have cancelled flights due to the freezing temperatures, some airport staff are braving the harsh conditions to keep people moving.
Columbus International Airport, in Ohio, shared a video showing an employee de-icing a plane on the runway.
The temperature in Columbus has fallen to -18C.
Skip Twitter post by @columbusairport
Shout out to all airport employees who are working outdoors today during the #polarvortex! We appreciate everything you do! ?: Gina K pic.twitter.com/x4KWdAAP0l
— John Glenn Intl (@columbusairport) January 30, 2019
End of Twitter post by @columbusairport
An American Airlines spokesman told USA Today that they have set up "mobile warming vans" for their ground staff at Chicago's O'Hare International Airport.
While United Airlines are reducing the amount of time workers spend out on the runway.
Sarah McMullen works at a hospital in Indianapolis, Indiana, where it is forecast to hit -23C (-10F).
Sarah told the BBC: "Emergency personnel and other hospital staff, such as myself, are required to go out to work even when there's an advisory which restricts travel."
She admits to feeling nervous about commuting in the cold.
"I've got blankets in the car, an overnight bag packed, and several layers prepared to wear during the maybe 20 minutes I'll spend outside all together."
Sarah is part of the team that receives patients from the ambulance outside the doors to the hospital.
"It is sometimes not a short process, so we will have to be innovative about how we keep ourselves and the patients warm.
"But medical emergencies happen whatever the weather, so we have to be here to make sure people can get treatment."
While Sarah says the cold will be a "challenge", she admits that it is also a bit "exciting to see how cold its gets".
'The colder the better'
Not everyone is worried about the cold. Dave Giacomin is thrilled the temperature has dropped.
He is an ice climber who runs a business helping people prepare for high-altitude mountaineering.
"I am currently preparing for a big climb up Mount Katahdin, in Baxter National Park, Maine," Dave says. "This cold weather is great for me. The colder the better!"
Dave is used to extreme cold temperatures and says "comparatively this is pretty mild. It's all relative".
Dave knows that most people won't want to venture outside while it's so cold.
"People see what I am doing and call me nuts. But I look at people sat inside on the couch and think they're nuts. I'm out living my life, even if it is cold!"