Many people don't realize how easily fire propagates when the forest gets really, really dry.

Some years ago, I was out hiking in the local mountains and I thought - "just too dry. This will be my last trip until we get some rain this fall." Forty-eight hours later, a 21,000 acre fire was started, and went wildly out of control, the result of ricochets from some target practice. I have heard of fires started by sunlight focused through pop bottles, but I am not sure about that.