Forest fire is common in places around the world where climates are moist enough to allow the growth of trees and shrubs, but have extended dry, hot periods. The most noted areas on Earth for wildfire include the vegetated areas of Australia, Western Cape of South Africa and throughout the dry forests and grasslands of North America and Europe.
Wildfires in forests and grasslands in North America are particularly prevalent in the summer, fall and winter, especially during dry periods with an increase in dead fuels and high winds. That period of time is called the wildfire season. Western U.S. fires tend to be more dramatic during summer and fall while Southern fires are hardest to fight in late winter and early spring when fallen branches, leaves, and other material dry out and become highly flammable.
Because of urban creep into existing forests, forest fires can often lead to property damage and has the potential to cause human injury and death. That "wildland urban interface" is a growing zone of transition between developing areas and undeveloped wildland. It makes fire protection a major concern for state and federal governments.
Millions of dollars are spent annually on fire protection and training fire fighters in the United States. An endless list of subjects on how wildfire behaves are collectively called "fire science". I want to very briefly introduce you to some concepts, terminology and web sites where you can explore the subject of wildfire at your leisure.
A Wildfire in the Southern United States - Photo by Steve Nix, Licensed to About.com