A change in wind direction has pushed a major wildfire away from Denver, but thousands of homes across the US state of Colorado remain at risk from fierce blazes fuelled by dry conditions.

About 6,000 homes southwest of Denver were evacuated before a fire engulfing more than 30,400 hectares (75,900 acres) shifted south, destroying defences built by firefighters.

"I think it's going to be a long time before we make significant advances in containment," said Joe Colwell, spokesman for the US Forest Service. "This is a weather-controlled fire right now."

The Denver Post newspaper reported that the blaze was only 5% contained and still threatened thousands of homes built in the Front Range foothills.

A light rain late on Monday only sprinkled the edges of the fire, which was started by an illegal campfire on Saturday in the Pike National Forest, 88 kilometres (55 miles) southwest of Denver.

The blaze is the worst of nine currently raging across Colorado.

Tinder

The Colorado Springs Gazette says the heatwave is expected to cool in the next few days but dry lightning is forecast for Wednesday - a further threat to the tinder-dry forests.

Colorado is being tested by fire like it has never been tested before

Bill Owens Colorado Governor

"The trees in the forest are drier than what you'll find in a lumber store," said Terry McCann of the US Forest Service.

The communities of Roxborough, Perry Park and Buffalo Creek are all on alert as the fire approaches.

Another blaze - covering 3,320 hectares (8,300 acres) - has destroyed 24 homes and sent residents fleeing in Glenwood Springs in western Colorado.

Firefighters have been using aircraft to try to douse the blazes, which have blanketed Denver and other areas with smoke and ash.

The National Guard and civilian volunteers have been helping fire crews to try to contain the flames.