The evacuation orders cover about 250 homes in Stillwater and Sweet Grass counties, fire information officer Pat Cross said Thursday. The wildfire was about 100,000 acres, or about 156 square miles.
Some structures have burned, but authorities don't know if they were homes or outbuildings, said Dixie Dees, another fire information officer.
The temperature Thursday was expected to stay in the 60s and low 70s, much cooler than Wednesday's windy 80-degree weather, but wind gusts around 20 mph were possible.
"The good news is that it is cooler, finally," Cross said. "So we hope the burning will be a little less active."
The Stillwater Mine called off its night shift Wednesday and Thursday day shift for about 200 workers because of smoke from the fire and concern about traveling conditions. Interstate 90 was temporarily closed between Livingston and Columbus.
The fire camp used as a base of operations was evacuated at 4 p.m. Wednesday because of encroaching flames, Cross said.
People who had not already left Wednesday were being called by emergency services and told that the situation was deteriorating, Sweet Grass County officials said.
"We're not going to take you out in handcuffs," Undersheriff Jerry Mahlum told residents at a public meeting. "We are going to ask you to sign a waiver that you've been warned and to let us know the next-of-kin you want notified."
Weather conditions were better at a wildfire in Washington.
Wet and cool weather helped slow the growth of a large wildfire in southeastern Washington and winds spawned by a cold front helped push some smaller fires back on themselves, but a windy forecast may make the reprieve short-lived.
Rainfall was reported Wednesday near a 67,000-acre fire complex in the Blue Mountains. The fire was 20 percent contained, and 1,175 firefighters were on the job. But a warmer, drier weather forecast, with highs rising into the 90s by Sunday, could refuel the blaze.
In California, firefighters made progress Thursday in battling a 2,000-acre wildfire in the San Bernardino National Forest.
About 1,230 firefighters took advantage of mild winds and an increase in humidity overnight by building lines and setting backfires.
The pre-dawn weather conditions "really helped slow down the fire," said U.S. Forest Service spokeswoman Carol Beckley.
The blaze was 60 percent contained Thursday morning, with full containment predicted by early Friday evening.