What is the main reason for seasonal variations in climate?

The main reason for seasonal variations in climate is the tilt of the Earth's axis as it orbits the sun. The Earth's axis is tilted at an angle of approximately 23.5 degrees, and this tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year. During different seasons, the Northern and Southern Hemispheres are tilted either toward or away from the sun, leading to changes in temperature and daylight.

For example, when the Northern Hemisphere is tilted toward the sun, it experiences summer with longer days and warmer temperatures, while the Southern Hemisphere experiences winter with shorter days and cooler temperatures. Conversely, when the Southern Hemisphere is tilted toward the sun, the reverse occurs. This axial tilt, combined with the Earth's orbit around the sun, is the primary factor driving the seasonal climate changes we observe.

Other factors, such as distance from the equator, changes in ocean currents, and variations in land use can influence regional climates and contribute to weather patterns, but they are secondary to the impact of the Earth's axial tilt regarding seasonal variations.