2 Answers

It's been around so long that few people take it seriously. But the claim that chatting on the phone in a thunderstorm can electrocute you is no urban legend. A bolt of lightning that strikes a telephone line can cause an electrical surge to shoot through the wires and enter a handset.The odds of this are relatively small, and most phone companies have protective measures in place. Still, the risk exists, and the National Oceanic and Atmospheric Administration recommends that people avoid using telephones and other appliances during electrical storms.

http://www.nytimes.com/2005/01/04/health/04real.html

I've always understood that it was dangerous to talk on the phone during a lightening storm, a corded phone anyhow but what about a cordless? I have no idea.....