Here’s a simplified version of your passage using sixth-grade vocabulary:
The Great Fire of 1910
For two scary days and nights, August 20 and 21, 1910, a huge fire burned across three million acres of untouched forest in northern Idaho and western Montana. Many people thought the world was coming to an end, and unfortunately, 86 people lost their lives.
Before the great fire of 1910, people in Coeur d'Alene, Idaho, and other nearby areas were told to leave by train, especially women and children. Forest Supervisors and local groups tried to fight the fire with the limited resources they had, including recent college graduates in forestry, forest rangers, and workers from mines and lumber camps. The forest service believed that over 100 smaller fires were started by hot pieces of coal from trains, showing how hard it was to control the big fire.
The Great Fire of Coeur d'Alene, which was part of the 1910 fires, was finally put out when a cold front brought heavy rain and some early snow, stopping the dangerous flames. The fire lasted for several days and was driven by strong winds and dry weather, but the change in weather helped get the fire under control.