A thunderstorm, or an electrical storm, is a form of weather characterized by the presence of lightning and its attendant thunder. It is usually accompanied by copious rainfall, hail, or, on occasion, snowfall in the winter months (which is sometimes known as thundersnow).
Thunderstorms can happen anywhere in the world, with the greatest frequency in tropical rainforest areas, where they may occur nearly daily. In temperate regions, they are most frequent in summer, though can occur in cold fronts at any time of year.
Thunderstorms form when significant condensation, resulting in the production of a wide range of water droplets and ice crystals, occurs in an atmosphere that is unstable and supports deep, rapid upward motion.
This often occurs in the presence of three conditions: sufficient moisture accumulated in the lower atmosphere, reflected by high dewpoint temperatures; a significant fall in air temperature with increasing height, known as a steep lapse rate; and a force such as mechanical convergence along a cold front that will focus the lift.
Thunderstorms have had a lasting and powerful influence on early civilizations. Romans thought them to be battles waged by Jupiter, who hurled lightning bolts forged by Vulcan.
Thunderstorms were associated with the Thunderbirds, held by Native Americans to be a servant of the Great Spirit. In more contemporary times, thunderstorms now have taken on the role of a curiosity. Every spring, storm chasers head to the Great Plains of the United States and Canada's prairie provinces to explore the visual and scientific aspects of storms and tornadoes.