The Hells Canyon Wilderness Area straddles the border of northeastern Oregon and western Idaho and comprises the Hells Canyon of the Snake River. The canyon is over 2,400 meters (8,000 feet) at its deepest. The area includes 68 miles of the Snake River. The area is located about 60 miles northwest and down river from Boise, Idaho, the main urban center for the region.

Data comparing the best and worst visibility days at Hells Canyon show poor visibility most often occurs in the winter, when air stagnation events create inversions conditions cause pollutant levels to rise. During these episodes, visibility is impacted by higher levels of nitrates and sulfates, which contribute to the formation of fine particulates. In the summer, visibility impairment occurs less frequently. Visibility impairment in the summertime is due to higher levels of organic matter, attributed to wildland fires.