Lightning is the transfer of significant charge between two charged objects. Lightning discharges can occur cloud-to-cloud, cloud-to-air and cloud-to-ground. Cloud-to-ground lightning has the greatest impact on our everyday lives. A lightning strike can kill, destroy equipment, start fires and be responsible for as much as 70% of typical power outages.

The awesome power of the lightning stroke originates in the thunderstorm cloud where charges somehow become separated. Since the ground beneath the cloud has far fewer negative charges on it than the bottom of the cloud, there is an attraction between the ground and the bottom of the cloud.

Even though the negative charges all move from cloud-to-ground, the bright flash of lightning moves from ground-to-cloud in a speedy 1/10,000 of a second, moving 61,000 miles per second! The super-heated air expands outward explosively, producing the shock wave we hear as thunder. The bright flash of glowing air is called the return stroke since it moves from ground-to-cloud, opposite to the moving charges.

There is quite a lot of energy in a lightning stroke, about 250 kilowatt-hours. With that amount of energy, you could lift a 2000-pound car 62 miles high! A lightning strike to an unprotected building packing 100 million volts of electricity has the force to rip through roofs, explode concrete walls, resulting in fire and total property loss.