Lightning is the visible discharge of static electricity within a cloud, betweenclouds, or between the earth and a cloud. It is one of natures most destructive forces.Lightning is the largest single cause of fire in suburban and rural areas, and it killsmore people than tornadoes, hurricanes, and floods combined. Lightning also causesmore than 80% of all accidental losses of livestock. Damage results in three ways: Electromagnetic fields from the lightning stroke, Voltage differentials in grounding systems, and Structural damage from heat or mechanical forces. The damage can be attributed to insufficient direct stroke protection, inappropriategrounding and bonding, and deficient transient voltage surge suppression (TVSS) protection.The following sections will describe the basic nature and action of lightningand consider the measures needed to protect buildings, equipment, livestock, trees, andpeople from lightning.