A thunderstorm is formed from a combination of moisture, rapidly rising warm air and a force capable of lifting air such as a warm and cold front, a sea breeze or a mountain. All thunderstorms contain lightning. Thunderstorms may occur singly, in clusters or in lines. Thus, it is possible for several thunderstorms to affect one location in the course of a few hours. Some of the most severe weather occurs when a single thunderstorm affects one location for an extended time.
Lightning is an electrical discharge that results from the buildup of positive and negative charges within a thunderstorm. When the buildup becomes strong enough, lightning appears as a "bolt". This flash of light usually occurs within the clouds or between the clouds and the ground. A bolt of lightning reaches a temperature approaching 50,000 degrees Fahrenheit in a split second. The rapid heating and cooling of air near the lightning causes thunder.
Thunderstorms affect relatively small areas when compared with hurricanes and winter storms. Despite their small size, ALL thunderstorms are dangerous! The typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Of the estimated 100,000 thunderstorms that occur each year in the United States, about 10 percent are classified as severe. Thunderstorms can produce tornadoes, lightning, strong winds, heavy rains (which can cause flash flooding), and hail. Some thunderstorms can be seen approaching, while others hit without warning. It is important to learn and recognize the danger signs and to plan ahead.
Thunderstorms & Lightning Danger Signs:
- Dark, towering, or threatening clouds.
- Distant lightning and thunder.
Safety Rules Before:
- Check for hazards in the yard. Dead or rotting trees and branches can fall during a severe thunderstorm and cause injury and damage.
- Make sure that all family members know how to respond after a thunderstorm.
Safety Rules During:
If Indoors:
- Secure outdoor objects such as lawn furniture that could blow away or cause damage or injury. Take light objects inside.
- Shut windows securely and brace outside doors.
- Listen to a battery operated radio or television for the latest storm information.
- Do not handle any electrical equipment or telephones because lightning could follow the wire. Television sets are particularly dangerous at this time.
- Avoid bathtubs, water faucets, and sinks because metal pipes can transmit electricity.
If Outdoors:
- Attempt to get into a building or a car.
- If no structure is available, get to an open space and squat low to the ground as quickly as possible. (If in the woods, find an area protected by low clump of trees - never stand underneath a single large tree in the open.) Be aware of the potential for flooding in low-lying areas.
- Crouch with hands on knees.
- Avoid tall structures such as towers, tall trees, fences, telephone lines, or power lines.
- Stay away from natural lightning rods such as golf clubs, tractors, fishing rods, bicycles, or camping equipment.
- Stay away from rivers, lakes, or other bodies of water.
- If you are isolated in a level field or prairie and you feel your hair stand on end (which indicates that lightning is about to strike), bend forward, putting your hands on your knees. A position with feet together end crouching while removing all metal objects is recommended.
- DO NOT LIE FLAT ON THE GROUND!
If in a car:
- Pull safely onto the shoulder of the road away from any trees that could fall on the vehicle.
- Stay in the car and turn on the emergency flashers until the heavy rains subside.
- Avoid flooded roadways, debris and washed-out roads may make driving very dangerous.
Because light travels much faster than sound, lightning flashes can be seen long before the resulting thunder is heard. If you can hear thunder, you are in danger from lightning . To estimate the number of miles you are from a thunderstorm, count the number of seconds between a flash of lightning and the next clap of thunder. Divide this number by five.
Lightning Facts
- Lightning causes an average of 80 fatalities and 300 injuries each year.
- Lightning occurs in all thunderstorms; each year lightning strikes the Earth 20 million times.
- The energy from one lightning flash could light a 100-watt light bulb for more than 3 months.
- Most lightning fatalities and injuries occur when people are caught outdoors in the summer months during the afternoon and evening.
- Lightning can occur from cloud-to-cloud, within a cloud, cloud-to-ground, or cloud-to-air.
- Many fires in the western United States and Alaska are started by lightning.
- The air near a lightning strike is heated to 50,000 degrees Fahrenheit - hotter than the surface of the Sun! The rapid heating and cooling of the air near the lightning channel causes a shock wave that results in thunder.
Lightning Myths and Truths
Myth: If it is not raining, then there is no danger from lightning.
Truth: Lightning often strikes outside of heavy rain and may occur as far as 10 miles away from any rainfall. This is especially true in the western United States where thunderstorms sometimes produce very little rain.
Myth: The rubber soles of shoes or rubber tires on a car will protect you from being struck by lightning.
Truth: Rubber-soled shoes and rubber tires provide NO protection from lightning. The steel frame of a hard-topped vehicle provides increased protection if you are not touching metal. Although you may be injured if lightning strikes your car, you are much safer inside a vehicle than outside.
Myth: People struck by lightning carry an electrical charge and should not be touched.
Truth: Lightning-strike victims carry no electrical charge and should be attended to immediately. Contact your local certifying agencies for information on CPR and first aid classes.
Myth: "Heat Lightning" occurs after very hot summer days and poses no threat.
Truth: "Heat Lightning" is a term used to describe lightning from a thunderstorm too far away for thunder to be heard.
In recent years, people have been killed by lightning while:
- boating
- swimming
- golfing
- bike riding
- standing under a tree
- riding on a lawnmower
- talking on the telephone
- loading a truck
- riding a horse
- playing soccer
- fishing in a boat
- mountain climbing