What causes the fog in cemeteries?

This is an extremely common occurrence in California. The tombstones soak up water from the sprinklers or rain and then it evaporates at night. This is due to a combination of heat sources, including necrosol, which is the soil surrounding coffins because decay = heat.

I'm only commenting because the top answer is an OPINION that couldn't be further from the truth. I hope that person educated themselves a bit in the past 14 years.