Once a wildfire is started, it is usually easy to tell from the smoke that will rise up into the air. If there is wind, it will blow the fire in a general direction. If you are downwind of the blaze, then the fire is coming toward you. If you are upwind of it, you are probably safe.
Forces of Nature: ThinkQuest 2000 (Team #C003603)
http://library.thinkquest.org/C003603/english/forestfires/prediction.shtml
There’s really no way to predict when a fire will start, but hot, dry weather usually facilitates their inception.