The lightning-sparked Trail Ridge Fire southeast of Sula has grown from 12,504 acres to 13,200 acres and remains 0% contained, according to the Friday update.
The blaze is burning approximately five miles southeast of Sula and approximately 11 miles northwest of the Big Hole National Battlefield.
Fire managers report cooler weather on Thursday helped slow the spread of the fire.
The Trail Ridge Fire continues to burn at higher elevations near the Continental Divide and there is no current threat to private land and property.
There are closures in effect in the Bitterroot National Forest and the Beaverhead-Deerlodge National Forest.