Final answer:
Condensation of water vapor is the condition that causes storms to occur. When water vapor condenses, it releases energy that drives the formation of clouds and thunderheads, leading to the development of storms.
Step-by-step explanation:
The condition that causes storms to occur is the condensation of water vapor. When water vapor carried by convection condenses and forms liquid droplets, it releases tremendous amounts of energy. This energy causes the air to expand, rise, and cool, leading to the formation of clouds and thunderheads. The process of condensation and the release of energy drive the formation of storms, including thunderstorms and hurricanes.