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Published on: 2/13/2013 4:18 PM
What is Lightning?  The key ingredient that defines a thunderstorm is lightning.  Lightning causes thunder. Therefore, anytime thunder can be heard, the danger of lightning is real, whether you can see it or not.
Lightning is the visible vault of electrical ions from cloud to cloud, and cloud to earth. When storm clouds gather, violent air currents separate ever-present electrical charges. Lightning's compelling objective is to complete a path to the opposite charge in the cloud or earth. The path of a cloud to ground lightning strike is not completed by hitting the top of a house, building or tree, but must continue until it reaches earth. An object is struck because it is a better conductor than air and offers a better path to the ground. However, since the object struck is not an adequate conductor, heat is generated, resulting in fire or explosive damage.
Although the flash of lightning and resulting thunder occur at essentially the same time, light travels at 186,000 miles in a second, almost a million times the speed of sound. Sound travels at the relatively snail pace of one-fifth of a mile in the same time. Thus the flash, if not obscured by clouds, is seen before the thunder is heard. By counting the seconds between the flash and the thunder and dividing by "5," an estimate of the distance to the strike (in miles) can be made.
There is no moving away from lightning, at least not within the limits of the United States. There are from 40 to 80 lightning strikes per year within the average square mile in the U.S.  While thunderstorms and lightning can be found throughout the country, they are most likely to occur in the central and southern states. In a long-range (1959 to 1994) study of lightning-caused casualties (fatalities and injuries combined), and damage reports based on information for all states and the District of Columbia, California ranked 51, meaning the least number of  lightning incidents causing casualties or damage.  Lightning storms are unusual in the San Francisco Bay Area, where the air is stable and the ocean waters cold.
Lightning Facts:
  • According to the National Oceanic and Atmospheric Administration, lightning kills 55% more Americans than tornadoes and 41% more than hurricanes and floods combined.
  • Lightning causes a total loss to homes and other structures of 15 - 20 million dollars each year.
  • Many fires in the western United States and Alaska are started by lightning. In the past 10 years, more than 15,000 fires have been started by lightning.
  • The U.S. Department of Agriculture estimates that lightning causes over 80% of all accidental livestock deaths.
  • Lightning moves about 30,000 times as fast as a bullet.
  • Lightning is a tremendously powerful force and may contain 100 million volts and 200,000 amperes -- thousands of times as much power as in an electric house current.
Thunder and Lightning Storms Place People At Risk!
According to Ron Holle, a meteorologist at the National Severe Storms Laboratory one of the most dangerous situations for lightning is a "Bolt Out of the Blue." A B.O.B. can occur before or after a thunderstorm occurs, and gets its name because people may not even know a thunderstorm is forming.
The six most common dangerous activities associated with lightning strikes, in order, are:
  1. Work or play in open fields.
  2. Boating, fishing, and swimming.
  3. Working on heavy farm or road equipment.
  4. Playing golf.
  5. Talking on the telephone.
  6. Repairing or using electrical appliances.
  • PLAN in advance your evacuation and safety measures. When you first see lightning or hear thunder, activate your emergency plan. Now is the time to go to a building or a vehicle. Lightning often precedes rain, so don't wait for the rain to begin before suspending activities.
  • IF OUTDOORS...Avoid water. Avoid the high ground. Avoid open spaces. Avoid all metal objects including electric wires, fences, machinery, motors, power tools, etc. Unsafe places include underneath canopies, small picnic or rain shelters, or near trees. Where possible, find shelter in a substantial building or in a fully enclosed metal vehicle such as a car, truck or a van with the windows completely shut. If lightning is striking nearby when you are outside, you should:
    • Crouch down. Put feet together. Place hands over ears to minimize hearing damage from thunder.
    • Avoid proximity (minimum of 15 ft.) to other people.
  • IF INDOORS... Avoid water. Stay away from doors and windows. Do not use the telephone. Take off head sets. Turn off, unplug, and stay away from appliances, computers, power tools, & TV sets. Lightning may strike exterior electric and phone lines, inducing shocks to inside equipment.
  • SUSPEND ACTIVITIES for 30 minutes after the last observed lightning or thunder.
  • INJURED PERSONS do not carry an electrical charge and can be handled safely. Apply First Aid procedures to a lightning victim if you are qualified to do so. Call 9-1-1 or send for help immediately.



For More Information Please Contact:
Office of Emergency Services
55 W. Younger Avenue
Suite 450
San Jose, CA 95110
Fax: 408-294-4851
Phone: 408-808-7800