A series of devastating wildfires in Portugal have killed 64 people since June. In August, Canada had its worst fires since 1958, and the deadliest wildfires in the history of California raced across the forests and the vineyards of the Napa Valley in October. More than 5,700 buildings have been destroyed, 213,000 acres of land scorched and 41 people have died so far. Why are they so devastating?
