Last updated on November 27th, 2010
Lightning Strike Density Map of the United States
Lightning Strike Density Map of the World
Be safe during a Lightning Storm
The highest priority in weather preparedness is awareness.
As most of us know, thunderstorms are common in the spring and summer months, but can occur during any time of the year. They typically develop from rising warm air heated by the sun, growing in height to become towering cumulus clouds.
The bottom, or base of a thunderstorm cloud will develop an electrical charge which then will try to discharge itself to the ground below. A ‘leader’ or leaders form and may branch out as it approaches the ground in search of a discharge point. A conductive ‘streamer’ will then shoot up from an object attached to the ground, usually a high point within the area, and will reach up and meet with the leader to create an often dramatic and powerful return stroke of bright lightning.
A Lightning bolt instantly heats the air around it to about 36,000 degrees F, hotter than the sun, which compresses (explodes) the air around it to create a supersonic shock wave, which is what we hear as thunder.
The less common ‘positive’ bolt of lightning (about 5% of all strikes) will discharge about ten times the energy as a ‘negative’ bolt, and typically comes from the top of a very large anvil type thunderhead and reaches out for miles and miles into the blue sky before it finds a pathway to ground.
If you can hear thunder, then you are in striking distance of lightning. The best and safest place to be during a thunderstorm is inside of a safe building (with a roof, walls and a floor) which has lightning rod protection on it’s roof. The rod is mounted at the highest point which is usually struck first by lightning. If struck, the electrical charge is carried from the rod down a grounding wire into the ground where it dissipates.
With or without lightning rod protection, stay away from anything electrical like phones, computers, TV and also stay away from plumbing like sinks, tubs, or shower because lightning often chooses these metal pathways to reach the ground.
Another safe place to be during a thunderstorm is in an enclosed safe car with a metal roof. If struck, the charge will carry around the outside of the metal skin of the car and discharge across to the ground. Be sure that you are not touching anything metal in the car.
You are not safe anywhere outside in a thunderstorm. Period. If you are unfortunately caught outdoors, get to a safe building or vehicle. Otherwise stay away from the tallest trees, stay out of open fields, away from the top of a hill, away from fences, and away from water. Seek out a lower place or a short stand of trees amongst the taller trees.
In the United States, lightning has killed nearly 90 people per year on average since 1959, while more than 200 people are injured each year by lightning.
Don’t become a statistic. Stay aware of the weather around you, look up at the sky once in a while, and get yourself a NOAA weather radio.