Faced with an icy polar vortex, US President-elect Donald Trump has announced plans to move his upcoming inauguration indoors.

Traditionally, ceremonies are held outdoors, most commonly on the marble steps of the Capitol Building in Washington, DC.

But with meteorologists predicting it will be one of the coldest Inauguration Days in recent history, Trump decided on Friday that a slight change in location would be necessary for safety reasons.

"Arctic storm is sweeping across the country. I don't want to see people hurt in any way," Trump wrote on his platform, The Truth Society.

"This is a dangerous environment for tens of thousands of law enforcement officers, first responders, police K9s and even horses, as well as hundreds of thousands of supporters who will be out there for hours."

Trump's ceremony, scheduled for Monday, will now take place beneath the Capitol Rotunda, whose curved sandstone walls are covered in paintings of American history.

Only one president has been sworn in inside the Capitol Rotunda: Trump's fellow Republican, Ronald Reagan.

Reagan's second inauguration in 1985 was also one of the coldest, exceeding even Monday's expected freezing temperatures. The weather was hovering around -14 degrees Celsius, or just 7 degrees Fahrenheit, with a chilly wind making the air feel even colder.

The National Weather Service expects temperatures to reach a high of -6 degrees Celsius (22 degrees Fahrenheit) on Monday.

Trump compared his situation to Reagan's in a social media post on Friday. He also addressed the issue of capacity in a limited space like the rotunda.

Under the original plan, about 250,000 guests had tickets to watch the inauguration near and around the steps of the Capitol.

Trump confirmed that "dignitaries and guests" will still come to the rotunda with him to witness the ceremony in person.

"This will be a great experience for everyone, especially the large television audience!" Trump wrote.

But other in-person attendees are encouraged to head to the First Capitol Arena, where the inauguration will be broadcast live.

"Once I'm sworn in, I'll be joining the crowd at Capital One," Trump added. He also plans to hold a "victory rally" there on Sunday.

The U.S. Capitol has hosted 55 different inauguration ceremonies, 34 of which were held on the East Portico (the colonnade on the exterior of the building).

Relatively few ceremonies were held indoors, but when ceremonies were moved indoors, both the Senate chamber and the House chamber were used as backdrops.

The cold weather has wreaked havoc on ceremonies that used to be held outdoors. In 1873, for example, President Ulysses Grant had soldiers fall around him, the icy wind making his speech difficult to hear.

Historians speculate how much the damp conditions on Inauguration Day played a role in the death of William Henry Harrison, who died of pneumonia just a month after becoming president.

His inaugural address was the longest in American history, and his time in office was the shortest.