Three people are missing and nearly 1,000 homes were destroyed and hundreds damaged in the fires, the cause of which is still unknown.

For those who escaped the blazes, snow and shivering temperatures are compounding the misery.

The blazes burned through at least 9.4 square miles (24 square km) on Thursday and firefighters eventually brought it under control on New Year's Eve.

The fires, in and around the drought-hit areas of Louisville and Superior - between Denver and Boulder - had been fanned by winds of up to 105mph that helped flames leap to new ground.

Tens of thousands of people were ordered to flee, many escaping through thick smoke as the fires approached.

And as the remains of properties were still smouldering on New Year's Day, the snow began to fall.

Families have been returning to their neighbourhoods to find burnt-out shells of their homes. In some streets, homes were reduced to smoking ruins, but other homes survived almost unscathed.

A historic drought and heatwaves have made wildfires harder to fight in the western US, with nine-tenths of Boulder County in severe or extreme drought having seen no substantial rainfall since mid-summer.

Keith Musselman, a snow hydrologist who lives in the region, said of the late snowfall: "With any snow on the ground, this absolutely would not have happened in the way that it did."

The fast-moving blaze reduced some communities to just "smoking holes in the ground", according to Boulder County Sheriff Joe Pelle.

Despite the enormity of damage, only seven people, including at least one first responder, were injured by the wildfire.

The homes of the three people missing have been destroyed and lie under hot debris and eight inches of snow, the sheriff said.

"It's all fallen in and it's now covered with eight inches of snow. So search and recovery efforts are hampered substantially," he said.

"What we're doing tomorrow is bringing in cadaver dogs to help investigators see if we can pinpoint if in fact, there are human remains, if we can't pinpoint where they would be and recover them safely.

"Right now it's not even safe to step into the scene. We don't know what's underneath. We don't know about the heat or anything else.

"So I have suspected we would have loss of life just based on the size of this fire and the speed and the ferocity. I think it's miraculous that if it is three, it was three and not a hundred or hundreds."

Authorities are still investigating what started the blaze, which was reported just after 11am local time on Thursday.

Evacuations were ordered for both Louisville and Superior, which are around 20 miles northwest of Denver and home to around 34,000 people.

Surrounding these areas are towns filled with shopping centres, parks and schools.

"For 35 years I walked out my front door, I saw beautiful homes," said local resident Eric House said.

"Now when I walk out - my home's standing - I walk out my front door and this is what I see," Mr House added.

When she returned to her home, Cathy Glaab found it had been turned into a pile of charred and twisted debris. It was one of seven houses in a row that were destroyed.

"The mailbox is standing," Ms Glaab said through tears. She added: "So many memories."

For the thousands of residents whose homes survived the wildfire, Red Cross shelter volunteers have been distributing electric heaters as utility crews are struggling to restore gas and electricity.

Extreme weather has also been taking hold in other parts of the US, with heavy snowfall disrupting road travel in the Pacific Northwest to California, and intense thunderstorms across the south damaging homes and buildings in Alabama.

The US National Weather Service has warned that long-awaited snow is expected to arrive across the Midwest, with as much as nine inches (22cm) expected to fall within hours.

"Hazardous travel conditions will develop this evening and continue into tonight," warned the National Weather Service in Grand Rapids.