The Sweet Grass Hills are in a class II airshed, as set by the State of Montana. Air quality is good to excellent in the higher elevations. Dust clouds can periodically be observed on the surrounding plains during dry periods due to agriculture practices and from vehicle traffic on unpaved roads. Particulate concentrations are highest during spring and summer due to farm operations, construction activities associated with the oil and gas industry, exhaust emissions from heavy equipment, spraying of noxious weeds and venting of casinghead gas associated with oil production.