File:Burn scars in central Alaska (false color) (MODIS 2015-09-11).jpg

English: The 2015 Alaskan wildfire season has become the second-worst year on record, with more than 5.2 million acres (2.1 million hectares) consumed through the end of August. The worst year on record � 2004 � saw 6.5 million acres burn, according to statistics cited by the Department of Natural Resources Division of Forestry and the University of Alaska Fairbanks. During an average year, 800,000 acres are lost to fire.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA�s Aqua satellite passed over Alaska on September 1, 2015 and acquired this false-color image of the landscape. The image combines infrared and visible light to increase the contrast between burned areas, which appear black and vegetation (bright green). Bare land appears tan, clouds appear white and very cold areas � snow and high cloud � appears electric blue. Deep blue or black represents ocean water.

Most of the largest fires occurred in the boreal forests of Alaska�s interior as well as in the southwestern part of the state. Because few people and limited infrastructure were at risk in these areas, authorities allowed many fires to burn unchecked. A combination of unusually warm temperatures, dry conditions and severely reduced snowpack allowed the fires to become quite large, and an early start to the season also allowed large sizes, by giving them a few extra weeks to burn. Of the 768 fires tracked by authorities, 348 were triggered by human activity and 417 were triggered by lightning. However, the vast majority of acres burned � more than 99 percent � was caused by lightning-triggered fires.