Answer:
Tiltation of the earth
Step-by-step explanation:
Seasons occur because of the tiltation of the earth and is tilted at an angle of 23.5°. The earth continuously moves around the sun in its elliptical path. Due to this, the sunlight is incident on the earth at different times causing the four types of seasons namely, spring, autumn, winter and summer.
When the earth's imaginary axis of rotation is tilted towards the sun, then the summer season occurs and the opposite side experiences a winter season. During the summer season, the earth is farthest from the sun and this position is called Aphelion whereas during winter the earth and the sun are at its closest position and this is known as the Perihelion.
Since the earth comes closer to the sun in winter, it should experience hotter weather but it experiences cold weather due to its tiltation.