Before settlement of the area at the end of the 19th century , wildfires frequently burned through the local forests , especially the ponderosa pine forests on the eastern slopes . Due to fire suppression over the past century , the forests have become overgrown , and at higher elevations , they are further susceptible to summertime fires , which threaten surrounding life and property . In the 21st century , wildfires have been larger and more common in the Deschutes National Forest . In September 2012 , a lightning strike caused a fire that burned in the Pole Creek area within the Three Sisters Wilderness , leaving the area closed until May 2013 . In August 2017 , officials closed in the western half of the Three Sisters Wilderness , including of the Pacific Crest Trail , to the public because of 11 lightning-caused fires , including the Milli Fire . As a result of the increasing incidence of fires , public officials have factored the role of wildfire into planning , including organizing prescribed fires with scientists to protect habitats at risk while minimizing adverse effects on air quality and environmental health
Milli Fire
Milli Fire
Broken Top