Sheesh ... light from the sky starting a fire?

LOTS of reasonable explanations for this, and they happen all the time. (for example dry air lighting, even withOUT clouds around is irregular and rare but a staple of life in many parts of the world including the dry land farming area of the US)

One of the most unusual "natural" events was the spotting of a warship in the Great Lakes (cruiser?) during WW2. LOTS of people saw it, but it really wasn't there.

Cause? A unique atmospheric tunneling caused by a very strong inversion layer that carried the "image" from the gulf coast all the way up to Great Lakes (as I recall the image was visible from parts of Chicago). This kind of very rare atmospheric tunneling carring an image does happen, though not often, and usually only over a distance of 100 to 200 miles, not the great distance involved in the Chicago event, which makes it an unique event ... but it was still NOT an other worldly type of event, just a natural but rare phenomenon.