National Weather Service Weather Forecast Office

After all the recent thunderstorms over the past few weeks, it might be a good time to review lightning facts and safety. Lightning causes an average of 80 fatalities and 300 injuries each year. Over a dozen people have been killed or injured in Colorado so far this Summer.

How Lightning Forms

Lightning results froom the buildup and discharge of electrical energy between positively and negatively charged areas within a cumulonimbus cloud. Rising and descending air within a thunderstorm separates thes positive and negative charges. Water and ice particles also affect charge distribution.

A cloud-to-ground lightning strike begins as an invisible negatively-charged channel of electrically charged air (called a "step leader") moving from the cloud toward the ground.

Lightning Facts

• The air near a lightning strike is very briefly heated up to 50,000° F, 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. The very sharp cracking sound of thunder is the result of oxygen molecules being ripped apart. If you can smell ozone after a lightning strike you were close to the bolt.
• Lightning occurs in all thunderstorms; each year lightning strikes the Earth 20 million times.
• During a strong monsoonal burst, thousands of lightning strikes occur in a 24 hour period across western Colorado and eastern Utah.
• 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; many occur on golf courses.
• Lightning can occur from cloud-to-cloud, within a cloud, cloud-to-ground, or cloud-to-air.
• Many fires in the western United States are started by lightning.

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 often produce very little rain ("dry lightning").

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  vehicles provides increased protection if you are not touching 
                metal.

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. Most who die do so because their hearts have stopped. Apply
               CPR at once.

MYTH:   "Heat lightning" occurs during hot Summer days and poses no threat.
TRUTH: There is no such thing as "heat lightning". This is lightning from a thunderstorm too far
                away for thunder to be heard. 

Lightning Safety

• If outdoors, seek shelter immediately.
• Stay away from telephones (cell phones are OK), windows, and water.
• If in a hard-topped vehicle, stay inside. Convertibles and the beds of pick-up trucks are not safe areas.
• If outdoors, go to a ditch, ravine, or low-lying area (but avoid streams and creeks due to the potential of flash flooding).
• DO NOT SEEK SHELTER UNDER A TREE! This only increases your chance of being struck.
• Avoid being the tallest object. Crouch down on the balls of your feet and place your hands on your knees. Do not lie flat.
• If outdoors and part of a group, space yourselves at least 15 feet apart from each other.
• If outdoors, and your skin begins to feel tingly and/or your hair begins to rise, you are about to be struck. Get down immediately.
• If outdoors, also avoid metal objects such as fences or flag poles.
• If swimming in a pool, lake, or stream...get out of the water immediately.