Air-borne embers can travel tens of miles.<p>Birds can carry burning twigs (deliberately to spread fires to flush out prey).<p>Arsonists.<p>Lightning strikes.<p>Electrical problems: sparks, wires rubbing on trees, faulty wires, broken wires lying on the ground, etc.<p>Broken glass acting as magnifying glasses.<p>There are plenty of reasons for wide-spread outbreaks when conditions are 'just right' over extended areas for fires.