Smoke also continues to shroud the Kaibab National Forest north of Grand Canyon National Park where a lightning-caused fire on June 8 has slowed, allowing crews to progress in containment efforts.
In Washington County, the Jarvis Fire, 10 miles southwest of St. George, was 85 percent contained by Thursday.
Anne Stanworth, spokeswoman with the Bureau of Land Management, said full containment is expected Saturday.
The human-caused fire, which has burned 50,700 acres and cost $800,000 so far to fight, continues to keep Old Highway 91 closed between the Utah-Arizona state line and Gunlock Reservoir, where a helicopter base has been established.
Stanworth said the fire also is threatening communication towers and power lines in the area, including one that runs a repeater site for the Federal Aviation Administration.
The 264 firefighters made progress Thursday on the Jarvis fire, constructing firelines and conducting burn outs.
The human-caused Kolob Fire, north of Virgin in Washington County, has burned 17,750 acres, with 10,500 of them in the Kolob Terrace section of Zion National Park.
The Kolob Terrace Road and all hiking trails connected to the road are closed. All other roads in the park are open.
Tom Haraden, a spokesman for the park, said the fire, being fought by 300 firefighters, was 60 percent contained on Thursday and full containment is expected at 8 p.m. Saturday.
Significant progress was made Thursday on the Warm Fire on the Kaibab National Forest in Arizona, which is burning 14 miles north of the North Rim of Grand Canyon National Park.
Firefighters today will continue to contain the south and east flanks of the fire.
The 58,000-acre fire is being fought by an 837-member incident management team. It has cost more than $4.5 million to fight the fire.
Arizona State Highway 67 remains closed from Jacob Lake, Ariz., to the North Rim until further notice. U.S. Highway 89A from Kanab, to Bitter Springs, Ariz., is open.