A snowstorm in Iowa is hindering Republicans’ campaign plans.

A storm that is forecast to dump close to a foot of snow in parts of Iowa on Monday and Tuesday is upending the campaigning plans of some candidates as they try to make the most of the last week before the Republican caucuses.

Nikki Haley, who has been rising in the polls and is trying to establish herself over Ron DeSantis as the definitive alternative to former President Donald J. Trump, had to cancel an event in Sioux City on Monday because of “travel difficulties.”

Mr. Trump’s campaign “indefinitely postponed” an event in Ottumwa for the same reason. Mike Huckabee, the former governor of Arkansas, and his daughter Sarah Huckabee Sanders, the state’s current governor and former White House press secretary, had been scheduled to appear on the former president’s behalf but couldn’t make it to Iowa because of the storm.

The actress Roseanne Barr withdrew from a Trump campaign event scheduled for Tuesday, too. That event — in Boone, Iowa, about 40 miles north of Des Moines — will still be held, but with a far less prominent headliner, the former acting attorney general Matthew Whitaker.

And Vivek Ramaswamy — who has been maintaining a breakneck pace in Iowa, sometimes with four or five appearances a day — delegated one of his five events scheduled for Monday to his wife, Apoorva.

She campaigned for him in Indianola, just south of Des Moines, so that he could make it to a rally in Sioux City — more than 150 miles away in northwestern Iowa — two and a half hours later without flying.