As the graphic shows, people cause most wildfires. But lightning-ignited fires burn by far the most territory.
The highlights of NOAA's 2013 Spring climate summary.
The number of big fires has shot up since 1970, with the largest number occurring during the years with the highest temperatures.
From Hurricane Sandy to record heat, here is our list of the top 10 extreme weather and climate events of 2012.
A look at which states were hit hardest by extreme climate and weather events in 2011.
In 2006, wildfires burned seven million acres in the West, the equivalent area of five of the country's largest national parks.
In a desert state like Nevada, heavy rains promote plant growth but can lead to more wildfires.
In a forested state like Montana, hotter and drier years leave forests more susceptible to large wildfires.