Fires taking place in several states have kept the Central United States covered by smoke (top left). The smoke extends from the Gulf Coast of Louisiana and Texas, through Texas, north into the Midwest before crossing into Canada where the smoke covers southern Manitoba, Saskatchewan and Ontario. There are two isolated pockets of medium density smoke. The first extends from Minnesota southeast through Iowa and Illinois where it becomes obscured by cloud cover. The other medium density plume extends east to west from Louisiana to Texas. Most of this smoke is likely from the large wildfires in California. The Aerosol Optical Depth over the same region shows very high values as retrieved by MODIS (top right). On the other hand, smoke from the Rim fire continues to cover part of California and Nevada. According to Earth Observatory, Air quality reached unhealthy levels from Yosemite to the San Joaquin Valley, according to an air quality alert from the National Weather Service. People were advised to avoid strenuous outdoor activity or to remain indoors because fine particles in smoke can irritate the eyes and respiratory system and aggravate chronic heart and lung disease.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite acquired this view of the fire on August 31, 2013 (bottom left). Red boxes outline the active fire areas. The smoke is brown and smooth in texture compared to the bright white clouds; it was thick enough at the time to entirely block the view of the ground from space. By September 2, the Rim Fire had burned 228,670 acres (357 square miles), making it the largest fire in the United States so far in 2013. The fire was 60 percent contained and threatening 4,500 buildings. Eleven homes and 100 other buildings have been destroyed. The fire started on August 17 and is expected to be contained by September 20.