A season is a division of the year, marked by changes in weather.
Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth’s axis relative to the plane of revolution. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth’s surface, variations of which may cause animals to go into hibernation or to migrate, and plants to be dormant.
During May, June and July, the northern hemisphere is exposed to more direct sunlight because the hemisphere faces the sun. The same is true of the southern hemisphere in November, December and January. It is the tilt of the Earth that causes the Sun to be higher in the sky during the summer months which increases the solar flux. However, due to seasonal lag, June, July and August are the hottest months in the northern hemisphere and December, January and February are the hottest months in the southern hemisphere.
In temperate and polar regions generally four seasons are recognized: spring, summer, autumn, winter.In some tropical and subtropical regions it is more common to speak of the rainy (or wet, or monsoon) season versus the dry season, because the amount of precipitation may vary more dramatically than the average temperature. For example, in Nicaragua, the dry season is called Summer (Oct to May) and the rainy season is called Winter (Apr to Nov) even though it is located in the northern hemisphere.In other tropical areas a three-way division into hot, rainy and cool season is used.