NATGEO Lightning Facts
It is almost soothing to hear the low rumble of thunder off in the distance as a storm approaches, yet the very sound of thunder indicates that you are in immediate danger. The forward and backward reach of lightning far outruns your ability to hear its thunder. When you hear thunder (even faint thunder) you are in danger of a lightning strike. When the leading edge of a thunderstorm is within 10 miles you are at immediate risk due to lightning's out reach. In fact, many lightning deaths and injuries occur with clear skies directly overhead.