Driving through Tysons yesterday I noticed a thunderstorm approaching from the north with the tell-tale darkening skies on the horizon and even a few rumbles of thunder. Regardless of the approaching storm, many people were still outside jogging, walking and in some cases just hanging out. Driving for a mile along Gallows I counted 13 people outside, away from substantial shelter needed for the approaching storm. At that point I could actually see lightning!
With this being Lightning Safety Awareness Week, I have decided to lay out a few facts and dispel a few myths about lightning.
Lightning Statistics and Facts: On average per year in the United States, there are around 25 million lightning strikes. Each one of those strikes is potentially deadly, and lightning remains the third-highest storm related killer after floods and tornadoes with an average of 55 deaths per year. A number of injuries also occur each year with some of those victims experiencing life-long health issues. Here are a few stories from lightning survivors we posted earlier this week.
How hot is lightning? The heat varies on the strength of the strike and what it is traveling through, but it is about 20,000 degrees Fahrenheit (though it can reach up to 50,000 degrees). That's nearly five times hotter than the surface of the sun. This is actually what causes thunder as the bolt is so hot that it rapidly expands the air around it which causes a sound wave.
How do you estimate how far away lightning is from thunder? When you see lightning and don't hear thunder for a period of time, you know it wasn't right next to you, but how close was it? It has been accepted that the sound of thunder travels about a mile every 5 seconds. So if you see lightning, then don't hear thunder for 10 seconds, it's about 2 miles away.
What is heat lightning? Heat lightning is really just lightning in a storm that is too far away to hear thunder. Thunder can generally be heard for about 12 miles, so if the storm is farther than that, you will not be able to hear the thunder, but you will be able to see the lightning, particularly at night. I actually experienced this while on a walk with my family in Bethany Beach when I was younger. That storm really caught us off guard as we had to all run about a mile and a half back to the beach house. Just another experience that scarred me for life and a reason I am terrified of lightning to this very day.
Does lightning come up from the ground or down from the cloud? Lightning usually comes down from the cloud unless it is triggered by something such as a radio tower or tall building.
What is a "bolt from the blue"? Lightning can be triggered even when the thunderstorm is far away. This can happen when charge separation is large enough for a bolt to occur out of the anvil or back side of a thunderstorm. It can travel up to 25 miles away from the storm, which is a reason why activities should be halted for 30 minutes after the last thunder is heard.