They have a good sense of smell, so it's not out of the question that they may smell fire, and may be looking for a good deep burrow to hide in. Fire is a hazard in Africa as well, so they may have evolved some behavior to avoid being killed if the scent of fire is in the air.

I know that when there were grass fires fully 50 miles north when I was living in Cheyenne, we could smell them when the wind was right. If I can smell a grass fire that far away, the snakes can surely smell them at even greater distances.