Any of the four periods into which the year is divided: spring, summer, autumn, and winter. The seasons arise from the Earth’s axis being tilted, so that different latitudes receive varying amounts of sunlight over the course of the year as the Earth orbits the Sun. Astronomically, the seasons are taken to begin at the equinoxes (spring and autumn) and the solstices (summer and winter). Meteorologists regard the seasons as groups of three calendar months, spring in the northern hemisphere being March, April, and May, and so on. The seasons are reversed in the southern hemisphere, southern autumn corresponding to northern spring, and so on.

season:

Seasons are caused by the Earth’s axial tilt. At the summer solstice, the north pole is tilted at its maximum towards the Sun. Northern latitudes then receive the maximum amount of sunlight, and southern latitudes the minimum. The situation is reversed six months later, at the winter solstice. In between, at the equinoxes, everywhere on Earth receives equal amounts of sunlight.