To form, these storms require three basic ingredients: Moisture, unstable air and lift. Moisture in the air typically comes from the oceans—and areas near warm ocean currents evaporate lots of moisture into the air. Moisture in the air is also responsible for making clouds.
The sun rays reach the earth's surface at an angle of 90 degrees at the equator which is direct and is short as compared to the poles it's long and about 66.5 degrees to the south and north. In the tropics its falls as 23.5 degrees in the northern and southern hemisphere.
The sun rays that form a tangent to the northern hemisphere are at 0, 23.5, 66.5 degrees i.e tropics, temperate and poles. And same is for the southern hemisphere.
On June 21 the southern hemisphere has winter seasons as the amount of insolation that reaches the southern side is less due to the tilt of the sun.
