A thunderstorm isn't a storm.
=== Severe thunderstorms ===In the United States, a thunderstorm is classed as severe if winds reach at least 93 kilometres per hour (58 mph), hail is 25 millimetres (1 in) in diameter or larger, or if funnel clouds or tornadoes are reported
=== Tornadoes and waterspouts ===A tornado is a violent, rotating column of air in contact with both the surface of the earth and a cumulonimbus cloud (otherwise known as a thundercloud) or, in rare cases, the base of a cumulus cloud

