What makes a wildfire extreme?

Extreme wildfires are occurring more frequently in many (although not all) flammable ecosystems. However, what exactly is meant by extreme depends on the context, as fires may be increasing in extent, size, intensity, rate of spread, severity, and/or infrastructural and economic damage, and these different meanings of extreme fire are often conflated. Here, we explore what is meant by extreme wildfire and discuss some of the analytical challenges to understanding extreme fire behaviors. We also examine some examples of analyses that have appropriately differentiated extreme fires from other wildfires to better understand the drivers of extreme wildfires in the context of climate and global change.