According to the Lightning Safety Group (LSG), composed of lightning experts from many lightning-related backgrounds, if you can see lightning or hear thunder, you are already at risk. Louder or more frequent thunder indicates that lightning activity is approaching, thus increasing the risk for lightning injury or death.
Because lightning flashes strike the ground an average of approximately 25,000,000 times per year in the United States, it is impractical to expect the National Weather Service to warn every individual of every flash.
Depending on where a person lives or recreates, lightning can be considered the most dangerous weather hazard that many will encounter each year.
Lightning may travel more than 10 miles in front of or behind a storm. A flash hits the ground in more than one location nearly 50% of the time and 10% of the time hits when there is no rain in the immediate area and blue sky can be seen.
Although high winds, rainfall, and cloud cover often act as precursors to actual cloud-to-ground strikes, many lightning casualties occur before the storm arrives because people ignore these warnings and wait for rain to fall.
When thunderstorms are in the area but not overhead, the lightning threat can exist even though the sun is shining, it is not raining, and some of the sky is blue. Lightning may travel more than 10 miles in front of or behind a storm. A flash hits the ground in more than one location nearly 50% of the time and 10% of the time hits when there is no rain in the immediate area and blue sky can be seen.
Other lightning injuries occur after the perceived threat has passed. Generally, the lightning threat diminishes with time after the last sound of thunder or sighting of lightning, but may persist for up to 30 minutes.
Weather warning devices, such as the INO Weather Pro, help warn of lightning danger, but you should always use common sense and the warning provided by your own eyes and ears.