(CBS/AP) Searing, record-setting heat in the Western U.S. didn't loosen its grip on firefighters struggling to contain blazes in Colorado, Utah and other Rocky Mountain states.

Colorado has endured nearly a week of 100-plus degree days and low humidity, sapping moisture from timber and grass, creating a devastating formula for volatile wildfires across the state and punishing conditions for firefighters.

"When it's that hot, it just dries the fuels even more. That can make the fuels explosive," said Steve Segin, a fire spokesman for the U.S. Forest Service.

Much of Nevada, Utah, Wyoming and Colorado are under a red flag warning, meaning conditions are hot, dry and ripe for fires.