When cold air runs into warm air on a large scale it forms a cold front. If the warm air mass is unstable enough this can trigger thunderstorms, potentially strong ones. Given a few other conditions these storms can begin to rotate and produce tornadoes. Most strong thunderstorms are associated with cold fronts.
However, another significant source of tornadoes. This is a similar scenario to a cold front, only there is a dry air mass pushing into a moist one with little temperature difference. A dry line is even more effective at producing tornadoes than a cold front.
The Arctic and the Antarctica because it's to cold for them to form there!
Tornadoes are most common in a temperate climate but can occur in the tropics.
The result will most likely be a frontal low.
Hail and tornadoes are most often associated with cold fronts, but can occur with dry lines or, lest often, warm fronts.
Tornadoes are most likely to be associated with a cold front.
Most tornadoes occur in spring.
Tornadoes most often form along a cold front, but do occasionally form along warm fronts.
The Arctic and the Antarctica because it's to cold for them to form there!
Although tornadoes occur in all states, the state with the most tornadoes is Texas.
Most tornadoes occur in spring and summer.
Tornadoes can occur in any season but are most common in the spring.
Tornadoes are most likely to occur in a temperate to subtropical climate.
Tornadoes are most common in a temperate climate but can occur in the tropics.
The most violent tornadoes generally occur in North America.
Tornadoes are most likely to occur in the late afternoon and earl evening.
Tornadoes are most likely to happen in warmer climates because warm air has more energy than cold air. It is that energy that powers the thunderstorms that produce tornadoes.
Tornadoes and other forms of severe weather are most often associated with cold fronts. However, warm fronts and stationary fronts have on occasion produced tornadoes.