How does spring air form tornadoes?

There are several factors as to why spring is conducive to tornadoes. First, during the spring the earth is heating up. As a result the lower atmosphere heats up faster than the upper atmosphere. This leads to increased instability, making conditions ripe for strong thunderstorms. Second, there are large temperature contrasts that power large-scale weather systems and produce strong fronts. These fronts act as a trigger for severe thunderstorms which can spawn tornadoes. Finally, during the spring the upper levels winds are still strong from winter. The strong upper level winds produce strong wind shear, which gives thunderstorms the rotation they need to produce tornadoes.

Tornadoes can form at any time of year, but conditions are rarely as ideal as they are in the spring.