Seasons

The seasons are regular changes in weather and daylight that occur throughout the year. In many parts of the world, people experience four seasons: spring, summer, autumn and winter. These changes are not caused by Earth being closer to or farther from the Sun. Instead, they result from Earth's axis being tilted by about 23.5 degrees relative to its orbit around the Sun.

As Earth travels around the Sun, each hemisphere alternately tilts toward or away from it. When a hemisphere is tilted toward the Sun, sunlight reaches it more directly and the days are longer, producing warmer conditions. When it is tilted away, sunlight arrives at a lower angle, days become shorter and temperatures are generally cooler.

The two hemispheres therefore experience opposite seasons at the same time. The changing seasons influence ecosystems, agriculture and daily life. Many plants flower in spring, grow during summer, produce seeds or fruits by autumn and become dormant in winter. Animals also respond to seasonal changes by migrating, breeding, storing food or hibernating, depending on the species.

Near the Equator, seasonal differences in temperature are often small, and the year may instead be divided into rainy and dry seasons. In contrast, regions closer to the poles experience much larger seasonal variations in temperature and daylight. The dates marking the beginning of the astronomical seasons are linked to the equinoxes and solstices, which result from Earth's position in its orbit around the Sun.