Careless smokers are certainly one of the causes. I have seen several start due to trailer safety chains dragging pavement. Was told of a 1000 acre fire that was started by a coke bottle acting as a magnifying glass.
In the wind yesterday a smoker will have a cigarette blow out of their hand or mouth. Sometimes the head can blow off and start it off with the extremely dry conditions. Thats just one way
Sparks from a train brakes use to be one of the biggest cause of fires but dont if they have improved them or not but in high winds power lines slapping together in the wind cause a lot, but there are a million different reasons a fire will get started when you have the right conditions.