[Excerpted from text] When the forest litter is wet it is hard to start a forest fire: when dry it is easy, therefore a prerequisite of a forest fire is a drought. Drought has never been defined in definite terms, but the common meaning is long-continued dry weather, especially so long continued as to cause vegetation to wither.

[This publication is referenced in the "Synthesis of knowledge of extreme fire behavior: volume I for fire managers" (Werth et al 2011).]