In many places the weather changes during the year. These changes are called seasons. In the north and south there are four seasons in a year. At the North and South Pole, there are only two seasons. In tropical (热带) places near the Earth's equator (赤道), there are two seasons: a 'wet' season and a 'dry' season. Each season brings changes. They are important for plants and animals that live in different parts of the world.
Spring starts when the day and night are the same length. The weather gets warmer and sunnier. Trees and plants start to grow. Many animals have their babies in spring.
Summer begins on the longest day of the year. In the north this is on June 21 or 22. Summer is usually the warmest and sunniest time of the year. Fruit grows faster on trees and plants. Young animals grow bigger and stronger.
Autumn starts when the day and night are the same length again.
During autumn, the leaves change color and fall down from the trees. Some animals collect food before winter comes.
Winter begins on the shortest day of the year. In the north this is on December 21 or 22. The weather is colder and in some places there is lots of snow. Plants and trees stop growing. Some animals, like bats and bears, find places to hide and sleep. This is calledhibernation.
