Heavy snow and fierce winds have swept across Iowa, disrupting campaign events just days before the state is due to kick-off the 2024 Republican presidential race in earnest.
Forecasters are warning of life-threatening conditions over the coming days, including icy winds that could lead to frostbite in just ten minutes.
Parts of the state have already seen as much as 10in (25.4cm) of snow.
A blizzard warning is in place and wind chills up to -45F (-42C) are forecast.
The conditions have hindered candidates' efforts to make their final pitches to voters before the Monday caucuses, when Republicans in Iowa will be the first in the country to pick their preferred candidate for president in the 2024 election.
Donald Trump holds a commanding lead in the polls, but the margin of his potential victory could be key in building momentum and cementing his position as the clear frontrunner for the party's nomination.
Nikki Haley, the former US ambassador to the UN, and Florida Governor Ron DeSantis are vying to pitch themselves as the main alternative to Mr Trump. Both will hope a strong second place finish could establish them as his main challenger early in the race.
But all three campaigns cancelled events on Friday due to the weather, which is expected to bring dangerous conditions over the next few days.
There are concerns the conditions could impact turnout on Monday, as caucuses require voters to turn up in person at one of more than 1,500 locations around the state. And while this part of the US Midwest is accustomed to cold winter weather, the current conditions are extreme even by Iowan standards.
Most of the candidates have referenced the storm in campaign appearances and on social media, with Mr DeSantis asking voters at an event on Thursday to "brave the elements" and back him. Mr Trump had a similar message, telling supporters last week that his campaign will be hurt "if you stay home".
"I know it's asking a lot of you to go out and caucus," Ms Haley told supporters in a telephone town hall. "I will be out there in the cold."
One Iowan, Mike Powers from Ames, said that while he expects some elderly residents may choose to stay home, he believed the weather was unlikely "to have that much of an impact on turnout."
"There's so much at stake," he said, speaking on the sidelines of a DeSantis campaign event at a roadside barbeque restaurant near Des Moines. "Iowans take this pretty seriously, being a first-in-the nation caucus."
That assessment was echoed by Ethan Hughes, a 21-year-old student from Cedar Falls who has attended campaign events for all of the Republican candidates.
"I'll be out there, for sure," he said. "We get this weather sometimes. People want to caucus. They want to be out there. They think their civic duty is important."
While most analysts predict a victory for Mr Trump in Iowa, the polls suggest the battle for second place between Ms Haley and Mr DeSantis is much tighter. That result could play a major role in determining the future of both campaigns, which have spent heavily on political advertising here.
Most polls put Mr DeSantis several percentage points ahead of Ms Haley, but a new survey of caucusgoers released by Suffolk University on Thursday showed Ms Haley in the lead for the first time with 20% support compared to Mr DeSantis's 13%.
Both campaigns expressed confidence they would finish strongly, with Ms Haley's campaign staff telling the OceanNewsUK she would ultimately emerge as the clear alternative to Mr Trump. "I think there's a general feeling that this is now between Donald Trump and Nikki Haley," campaign spokeswoman Olivia Perez-Cubas said. "The field is consolidating."
Mr DeSantis, meanwhile, has ramped up his criticism of Ms Haley as well as the former president, telling reporters on Thursday night that he believes Mr Trump's various legal battles will eventually doom him in a general election.
"Do you want the 2024 election to be a referendum on legal issues?" he said. "That plays into the Democrats' hands."
Mr DeSantis and Ms Haley traded insults in a tense one-on-one debate earlier this week, as Mr Trump chose not to attend the CNN-hosted event and other candidates such as Vivek Ramaswamy failed to qualify.
The DeSantis campaign said on Friday that he would skip New Hampshire, where the next contest is being held after Iowa, and head immediately to Ms Haley's home state of South Carolina. His campaign said the move was intended to send a message that it is intent on performing well there.
A statement announcing the move also took aim at Mr Trump. "We hope [he] is ready for a long, scrappy campaign," it said. "Game on."
