In Colorado, 100-degree temperatures and near-zero humidity were helping the fires, the Denver Post reported.
The largest was in Larimer County, where more than 81,000 acres have burned. Another in a hiking area in Colorado Springs had consumed 2,000 acres, the Post said. Some 2,300 residents were evacuated Saturday, officials said.
To the north near the Rocky Mountain National Park, a fire broke out and destroyed 21 buildings, the report said.
In Utah, some 2,500 people were allowed back into their homes in Eagle Mountain and Saratoga Springs Saturday night, the Salt Lake (Utah) City Tribune reported.
Almost 600 homes had been evacuated as the Dump Fire, so-named because it was sparked by target shooters at a landfill, spread over some 6,000 acres, the newspaper said.
Officials said 500 firefighters were working to contain the blaze.
Various Utah communities also declared a ban on fireworks in the run-up to the July 4 Independence Day celebrations, the newspaper said.