If there isn't enough moisture, then no clouds will form.
Thunderstorms require moist air to form. That is where the rain comes from.
In order for thunderstorms to form the air must be unstable, which generally requires the air near the ground to be warm and moist. This warm, moist air provides the energy that powers thunderstorms. The warmer and more humid the air is, the more energy is available for thunderstorms.
Generally the air is moist as tornadoes require thunderstorms to form.
Evaporation.
Thunderstorms are more likely to form in areas that have large water bodies like the seas and lakes. Places that experience the convectional rainfall is the place that will experience thunderstorms on a regular basis.
Tornadoes need strong thunderstorms in order to form. Thunderstorms, especially strong ones require warm moist air to power them. Cold air simply does not have enough energy.
In the simplest terms, rising masses of warm, moist air trigger thunderstorms. Tornadoes need thunderstorms to form.
Air-mass thunderstorms form due to uneven heating of Earth's surface. As the surface heats unevenly, pockets of warm, moist air rise quickly, leading to the development of cumulonimbus clouds and thunderstorms. These storms are typically short-lived and localized.
No single air mass "causes" tornadoes. This is Tornadoes form within thunderstorms. Thunderstorms form best when there is plentiful warm, moist air. So, a arm, moist air mass is usually present. Significant tornado activity, however, usually results from the thunderstorms that form near the boundaries between air masses. Usually where a warm, moist air mass meets a cooler or drier air mass.
Thunderstorms in Florida form when warm, moist air from the Gulf of Mexico or the Atlantic Ocean converges with cooler air from the north or west. This warm, moist air rises and cools, forming clouds and eventually thunderstorms. Florida's warm climate and proximity to bodies of water make it a prime location for thunderstorm development.
No single air mass "causes" tornadoes. This is Tornadoes form within thunderstorms. Thunderstorms form best when there is plentiful warm, moist air. So, a arm, moist air mass is usually present. Significant tornado activity, however, usually results from the thunderstorms that form near the boundaries between air masses. Usually where a warm, moist air mass meets a cooler or drier air mass.
Antarctica is very cold while tornadoes can only form with thunderstorms, which require at least some degree of warm, moist air.