The cycle of seasons is caused by Earth's tilt toward the sun. The astronomical definition of the seasons relates to specific points in Earth's trip around the sun. The summer and winter solstice, the longest and shortest day of the year, occur when Earth's axis is either closest or farthest from the sun.
How do the seasons occur on Earth?
The tilt of the Earth means the Earth will lean towards the Sun (Summer) or lean away from the Sun (Winter) 6 months later. In between these, Spring and Autumn will occur. The North pole always points the same way as the Earth revolves around the Sun. The Earth's movement around the sun causes the seasons.
How do the four seasons occur?
The four seasons happen because of the tilt of the Earth's axis. At different times of the year, the sun's rays hit different parts of the globe more directly. The angle of the Earth's axis tilts the Northern Hemisphere towards the sun during the summer.