Why don't hurricanes and tornadoes develop in the same months?

Answer 1

They do, to some degree. Tornadoes occur year-round and are often produced by hurricanes. It is true though, that tornado activity usually peaks in spring while hurricanes usually peak in late summer. The difference is do to the different conditions that produce them.

Tornadoes most often form from extremely powerful thunderstorms called supercells. Supercells are most likely to form with very unstable air, wind shear, and colliding air masses of different temperatures. The atmosphere is most unstable when the lower atmosphere is very warm while the upper atmosphere is cold. Such instability is sometimes greater in the spring when the upper atmosphere has not warmed as much as in summer. Wind shear, or differences in wind speed and direction with altitude tends to be strongest in the winter and weakest in the summer. The in-between levels in spring are well-suited for supercells.

Hurricanes are a different matter. They depend primarily on warm ocean water, and the oceans take a long time to warm up. They are usually warmest in the late summer. The weak wind shear of summer also favors hurricanes. Strong wind shear prevents hurricanes from organizing and can just about tear existing hurricanes apart.

Answer 2

Hurricanes typically develop in the late summer and early fall months when ocean waters are warmest. Tornadoes, on the other hand, can occur throughout the year but are most common in the spring and early summer when there is a clash of warm and cold air masses. The differing mechanisms and atmospheric conditions required for the formation of hurricanes and tornadoes account for their occurrence in different months.