The wildfire burning near Hayden Creek, four miles from Coaldale, grew on Sunday due to heat according to the Fremont County Sheriff's Office.
The "Hayden Pass" fire is burning in the area of US Highway 50 and County Road 6 and grew to more than 5,000 acres by Sunday night.
An Air Quality Advisory went into effect at 9 p.m. for Fremont County, specifically for Canon City, Cotopaxi, Coaldale and Howard.
"If smoke is thick or becomes thick in your neighborhood you may want to remain indoors. This is especially true for those with heart disease, respiratory illnesses, the very young, and the elderly," said a Colorado Department of Public Health and Environment official.
U.S. Forest Service fire crews and Western Fremont County Fire crews will continue to battle the blaze throughout the night. Authorities said Sunday evening it is "well up the mountain" and "not posing any imminent danger at this time."
Pre-evacuation notices went out to people living along County Road 6 to Pole Mountain lane. The Hayden Creek Campground on Fremont County Road 6 has been fully evacuated.
Lightning sparked the fire on Friday. The public is asked not to call 911 to report the fire.