Arctic air blankets the US

>>> now we go outside, which depending on where you live, might take some stealing of yourself, given the air that has descended on a lot of our country. take, for example, nbc's kevin tibbles out in the cold tonight in chicago . kevin , good evening.

>> reporter: hey, why not? well, it will take a couple more frigid days to freeze the chicago river , but tonight temperatures here in chicago , new york and elsewhere are colder than they are in juneau, alaska. at one point, some 200 chicago firefighters battled a massive extra alarm warehouse fire in temperatures hovering just above zero. pouring on the water throughout the day, struggling with frozen hydrants and icy ladders.

>> the stress on us, i mean, we're firefighters and we're used to dealing with the cold.

>> reporter: an eerie scene of the ruins encased in ice. after a mild start to the winter in many places, this bitter cold has taken much of the nation by surprise. the coldest place in the u.s. today, a previous winner, international falls , minnesota at minus 20. but low temps gripped cities across the map. and for those working outside, time for precautions. as frostbite can set in after just ten minutes of exposure. servicing aircraft at rhode island 's tf green airport , critical, bone-chilling work.

>> the key is to keep moving. once you stand still , that's when you get cold.

>> reporter: nick vonek moves eggs at chicago 's market.

>> when it's this cold, i jut put on my snowsuit. otherwise it's just layers.

>> reporter: in pennsylvania, heating companies scramble to fix broken furnaces.

>> we're probably operating at 200% capacity right now. everybody is working double shifts and trying to get everybody heat.

>> reporter: and in new york city , street vendors shivered but cashed in on the cold.

>> hats, scarves, ear muffs , selling very well.

>> reporter: as for tourists visiting the nation's capitol this inauguration week, a bit of of a shock.

>> oh, my gosh, it is so cold.

>> reporter: how long is it going to last?

>> this unusually cold air is going to stick around into the weekend before a brief warmup early next week and then the cold air returns late next week.

>> reporter: the cold is good news for northeastern ski resorts hungry for snow. but some are finding it's just too cold to open, even for skiers. and, brian, more snow and cold in the forecast for the northeast, and midwest. i've got one other record to share with you tonight, as you shiver in new york, brian. another record was broken today in phoenix. it was over 80.

>> i knew you were going to do that to us. kevin tibbles in the city that doesn't scare easily. chicago , illinois in the cold tonight. kevin , thanks.