Lightning -- once one of nature's biggest killers --is claiming far fewer lives in the United States, mostly because we've learned to get out of the way.

In the 1940s, when there were fewer people, lightning killed more than 300 people annually. So far this year, 13 people have died after being struck, on pace for a record low of 17 deaths. Taking the growing population into account, the lightning death rate has shrunk more than forty-fold since record-keeping began in 1940.