A season is a division of the year marked by changes in weather, ecology and hours of daylight. Seasons result from the yearly orbit of the Earth around the Sun and the tilt of the Earth's rotational axis relative to the plane of the orbit. In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to go into hibernation or to migrate, and plants to be dormant. Red and green trees in spring During May, June, and July, the northern hemisphere is exposed to more direct sunlight because the hemisphere faces the sun. The same is true of the southern hemisphere in November, December, and January. It is the tilt of the Earth that causes the Sun to be higher in the sky during the summer months which increases the solar flux.
In the spring, seeds take root and vegetation begins to grow. The weather is warmer, and often wetter. Animals wake or return from warmer climates, often with newborns. Melting snow from the previous season, along with increased rainfall, can cause flooding along waterways, according to the Federal Emergency Management Agency (FEMA).
In the summer, temperatures may increase to their hottest of the year. If they spike too high, heat waves or droughts may cause trouble for people, animals, and plants. For example, in the summer of 2003, the high temperatures claimed more than 30,000 lives, according to Encyclopedia Britannica. Rainfall may increase in some areas, as well. Others may receive less water, and forest fires may become more frequent.
In the autumn, or fall, temperatures cool again. Plants may begin to grow dormant. Animals might prepare themselves for the upcoming cold weather, storing food or traveling to warmer regions. Various cultures have celebrated bountiful harvests with annual festivals. Thanksgiving is a good example. "Thanksgiving in the United States is a historical commemoration but it has a spiritual dimension strongly associated with homecoming and giving praise for what has been bestowed upon us," Cristina De Rossi, an anthropologist at Barnet and Southgate College in London, told Live Science.
Winter often brings a chill. Some areas may experience snow or ice, while others see only cold rain. Animals find ways to warm themselves, and may have changed their appearance to adapt. "In a similar way to the Autumnal theme, Winter festivals celebrate the return of the light during a time of deepest physical darkness," said De Rossi. The Indian festival of Diwali, for example, which takes place between October and November, celebrates the triumph of righteousness, and of light over darkness.