"When thunder roars, head indoors."

National Weather Service Meteorologist Valerie Meola said Sunday the old rhyme is the best advice one could heed when dealing with storms.In the aftermath of the death of Jose Lopez-Hernandez, 38, of Camden, New Jersey, who was struck by lightning Saturday night at Beltzville State Park, experts warn that the minute you hear thunder, you are susceptible to a lightning strike."You can see lightning pretty far off in the distance, but the thunder is really the significant threat," Meola said.Lightning strikes kill, on average, 73 people and injure 300 others, according to the NWS.There are 25 million cloud-to-ground lightning strikes occur in the United States each year.The chances of being struck by lightning in a lifetime are 1 in 12,000."The probability is low, but you have to remember that no place outside is safe during a lightning storm," said Devin Buzard, Beltzville State Park manager.Buzard said Saturday's incident was "very unfortunate" and that it is the only fatal lightning strike he has seen at his time at the park.Though one ground lightning strike can generate between 100 million and 1 billion volts of electricity, 90 percent of lightning strike victims survive, according to the NWS.Lightning develops from an attraction between positive and negative charges in the atmosphere, resulting in the buildup and discharge of electrical energy.Rapid heating and cooling of the air produces the shock wave that causes thunder.Meola said the ideal place to go in a storm is a building with electricity or plumbing or an enclosed, metal-topped vehicle with the windows up.People should also stay in shelter until at least 30 minutes after the last sound of thunder. More than 50 percent of lightning deaths occur after the thunderstorm has passed.She also urged not to underestimate the distance lightning can travel."Though a storm may be off in the distance, you can be struck by lightning from 10 miles away," she said.