More than 32,000 people have fled Colorado's second-biggest city because of raging wildfires that have hit six other US states.
Traffic and smoke choked the streets as people left Colorado Springs and a nearby US Air Force Academy.
Evacuation orders were issued for much of the city as the fire doubled in size to over 62 square kilometres. Some 800 firefighters have been deployed.
President Barack Obama is to tour the affected areas on Friday.
Just weeks into the northern hemisphere's annual wildfire season, there are also fires in Montana, Wyoming, New Mexico, Arizona, California and Utah.
In Utah, a body was found in the ashes of a fast-moving wildfire to the south of Salt Lake City.
Firestorm
At a press briefing on Wednesday morning, officials in Colorado said fire crews had worked through the night. But the blaze was only 5 percent contained.
Dry, hot temperatures are expected to continue across much of the USA this week, with little chance of rain.
"We do expect all of our lines to be challenged today," incident commander Richard Harvey said, adding that erratic winds could make their job harder.
One Colorado Springs hospital said it had treated about 20 patients in the last 24 hours for respiratory-related illnesses, a local newspaper reported.
The Waldo Canyon Fire, which began on Saturday, has been fanned towards Colorado Springs by winds of up to 104kmh.
"It was like looking at the worst movie set you could imagine," Colorado Governor John Hickenlooper said after surveying the fire from the air.
"It's almost surreal. You look at that, and it's like nothing I've seen before."
Heavy ash and smoke was billowing from the hillsides west of Colorado Springs and southbound traffic was temporarily closed on Interstate 25, which runs through the city.
Fleeing residents covered their faces with T-shirts to breathe through the smoke.
