IMHO...not only have wind turbine fires been caused by heat generated in the wiring; or from lightning strikes or by overspeed of the blades caused by wind gusts, etc.
http://www.windfarmfactsutah.org/PHOTOS.html
Something that I’ve not seen mentioned as a source of heat/fire, is the heat generated in the gearboxes of these things. A very steep gear ratio is required to harness the very slow revolutions of the propeller shaft, and step it up, through a series of gears, to the speed required to spin a generator at the revs per minute required to produce electricity. The pressure on that gear train has to be very high, and it surely results in a lot of heat being created.
This very type of heat generation in the harnessing of mechanical torque is why there are transmission coolers on trucks, and on cars used to pull campers and other loads. Also, the housing/fairing enclosing the gearbox and generator machinery actually traps most of this heat because the housing must be fairly tight to preclude bird nests, insects and their nests, etc. So the machinery is not even effectively air-cooled.
Not many reach temps sufficient to cause a fire, but I think the rise in air temperatures surrounding the turbines comes at least as much, if not more, from the heat generated BY the turbines themselves, than it does merely from disturbance of the air strata around them. Bottom line: The turbines innately are generators of heat, as well as electricity.