The blaze near the towns of Glenwood and Annabella in Utah's Sevier County, which began Tuesday, had burned nearly 600 acres, and Interagency Fire Center spokesman John Zapell said crews hoped to have it contained by Wednesday evening or Thursday morning.
Firefighters had contained two other fires further north, the 1,572-acre Ophir Creek fire and the 208-acre Wiley fire, The Salt Lake Tribune reported.
The High Park fire, northwest of Fort Collins, Colo., had consumed 65,738 acres, fire officials said, and a shift from what are called "red flag conditions" to cooler and less humid weather will make it easier to fight the fire, Fire Incident Commander Bill Hahnenberg said.
"We are going to be very aggressive," Hahnenberg said.
More than 1,900 firefighters were at work on the blaze, which is at 55 percent containment, fire officials said.
Some evacuees are expected to be allowed to return to their homes soon, Larimer County Sheriff's Office spokesman John Schulz said Wednesday.
The Arizona Republic reported Wednesday that two recently ignited fires in Arizona forests grew in intensity Monday, and that three smaller fires had been contained.
The Fox fire in Coronado National Forest had grown from 1,400 acres Monday to 3,400 acres Tuesday, and 180 people were fighting the fire. The Poco fire in the Tonto National Forest has grown from 3,200 acres to 3,700 acres, the newspaper said. Smaller fires near the Arizona towns of Globe, Superior and Garden Canyon have been contained.