Plunging temperatures wreaking havoc across the US and Canada can lead to frostbite on bare skin in only five to 10 minutes, experts are warning.
President Joe Biden has told President Volodymyr Zelensky the US will stick by Ukraine "for as long as it takes" in its war with Russia.
At least three people have died as a powerful winter storm moves east across the US, spawning tornadoes in southern states and coating others in snow.
The son of two Canadian billionaires has offered an additional C$25m ($18.34m; £14.95m) as a reward for information on his parents' killer.
A powerful storm has spawned tornadoes in the southern US and brought heavy snowfall and other extreme weather across the US and parts of Canada.
Democrats have cemented their control of the US Senate by winning a bitterly fought seat in Georgia, according to projections.
A gunman has killed up to 10 people in a Walmart supermarket in Chesapeake, in the US state of Virginia, police say.
Republicans have secured the 218 seats needed for a majority in the lower chamber of Congress a week after the midterm elections, the BBC's US partner CBS News projects.
Donald Trump has announced his third straight presidential bid, in an extremely rare attempt by a former US leader to recapture the White House after losing an election.
Rivalry between Donald Trump and Ron DeSantis has spilt open after the Republican ex-president came swinging out against his one-time acolyte on Thursday night.
Russia's unmanned Luna-25 spacecraft has crashed into the Moon after spinning out of control, officials say.
Donald Trump has confirmed that he will not take part in Republican presidential debates with his rivals in the race for the White House.