Autumn
Autumn is one of Earth's four seasons. It includes the months of September, October, November, and December. Autumn is also called fall.
Most areas of the world experience four seasons. They are spring, summer, autumn, and winter. The seasons occur because of the Earth's movement around the Sun. When the northern part of the Earth is leaning away from the Sun and the southern half is leaning toward the Sun, it is winter in the north and summer in the south.
Autumn begins when the Sun is at its midpoint in the sky. This occurs on September 22 each year. In autumn day and night each last 12 hours.
Autumn means means cooler temperatures. It is dark out longer in autumn than in the summer. The days and nights get colder. Frost covers the ground. Autumn is the time when farmers harvest their hay.
In autumn the leaves begin to change color. Summer and spring leaves are green because of a chemical called chlorophyll (KLOR-oh-fill). This chemical helps leaves grow.
In autumn leaves live off energy they've stored over the spring and summer. As the chlorophyll is used up leaves become yellow and orange. The bright reds and purples come from trapped sugar. The sugar turns color in colder temperatures.
If an autumn has many cloudy days, leaf colors will be dull. But an autumn full of sunny days will give us bright leaf colors. Soon the leaves dry out and fall off the trees. Winter is just around the corner.
Autumn has the least severe weather of any season. The last day of the season is December 20.