The seasons are caused by the tilt in the rotational axis of the Earth. This tilt in the direction of the sun or the opposite one determines the seasons. During the summer solstice this tilt is maximized in the Northern Hemisphere. At this time, the amount of sunlight reaching the Northern Hemisphere is the greatest. Similarly during the winter solstice, least amount of sunlight reaches the Northern Hemisphere.
As seen the seasons are inverted in the Southern hemisphere. The non tropical cyclone formation increases in the winter months because of the difference between cold air over land and the relatively warm air over the ocean. That is why there are more storms in winter as compared to summer.