Season

The year has different parts.

These parts are called seasons. The weather changes in each one. The sun stays up for different times.

Earth is tilted as it moves around the sun. This tilt makes the seasons. One part of Earth leans toward the sun. That part gets more light and heat. This makes it summer there. The other part leans away. That part gets less light. This makes it winter there. The two halves of Earth have opposite seasons. Seasons help animals and plants know when to grow.

A season is a part of the year.

Seasons change based on weather and daylight. They also change how much light reaches the ground.

Earth has a tilt. This tilt is about 23.4 degrees. As Earth moves around the Sun, this tilt stays in the same direction. This is called axial parallelism. Because of the tilt, one part of Earth leans toward the Sun. This part gets more direct sunlight. This makes it summer. The other part leans away from the Sun. It gets less light. This makes it winter. The two halves of Earth always have opposite seasons.

In the North, summer happens around June. In the South, summer happens around December. The warmest months can happen later than the summer start. This is called seasonal lag. It happens because oceans take time to warm up.

In some places, like the tropics, there are only two seasons. These are the wet season and the dry season. In other places, people see four seasons. These are spring, summer, fall, and winter.

A season is a way we divide the year. These divisions happen because of changes in weather and daylight hours.

Seasons also change how much light reaches the surface of the Earth. In many places, people recognize four seasons: spring, summer, fall, and winter.

However, other places see different patterns. Tropical regions often have a wet season and a dry season. Ecologists might even use a six-season model to describe how nature changes.

Seasons happen because of Earth's axial tilt. The Earth is tilted at an angle of about 23.4 degrees.

As Earth orbits the Sun, it keeps this tilt in the same direction. This is called axial parallelism. Because of this tilt, one part of the planet leans toward the Sun. That part receives more direct sunlight, which creates summer. The other part leans away and receives less light, creating winter. This is why the Northern and Southern Hemispheres always have opposite seasons.

Sometimes the warmest weather happens later than the actual start of summer. This is known as seasonal lag. It happens because the oceans take time to absorb and release heat.

In the Northern Hemisphere, the warmest months are often June, July, and August. In the Southern Hemisphere, the warmest months are December, January, and February. The Sun is highest in the sky during these summer months. This increases the solar flux, which is the amount of energy from the Sun.

People have tracked seasons for a very long time. Ancient Egyptians defined seasons by the flooding of the Nile River. They used three seasons: flood, growth, and low water. In India, people have used six seasons called Ritu for many centuries.

Roman times also show a four-season model. A writer named Varro described the seasons in his work. He even assigned specific dates to the start of each season. These historical ways of looking at the year helped people with farming and trade.

Seasonal changes affect almost all living things on Earth. In temperate regions, plants may go dormant to save energy.

Some animals might go into hibernation or move to new places during migration. The amount of sunlight changes how these living things act. Even the shape of Earth's orbit plays a small role. Earth reaches its closest point to the Sun in January. This is called perihelion. It reaches its farthest point in July, which is called aphelion.

These cycles connect the movement of our planet to the life around us.

A season is a division of the year based on changes in weather, ecology, and daylight hours. These cycles help us understand the rhythm of our planet. In many temperate regions, we recognize four distinct seasons: spring, summer, fall, and winter.

However, the way we define seasons depends on where you live. Tropical regions often experience only two seasons: a wet season and a dry season. Some ecologists use a more complex six-season model to describe nature. These models include stages like prevernal, vernal, estival, serotinal, autumnal, and hibernal.

Seasons are caused by the Earth's axial tilt and its orbit around the Sun. The Earth's axis is tilted at an angle of approximately 23.4 degrees. This tilt is also known as the obliquity of the ecliptic. As the Earth moves along its orbital plane, it exhibits axial parallelism. This means the direction of the axis remains parallel to itself throughout the year. The axis points toward Polaris, the North Star, all year long.

Because of this tilt, different parts of the Earth receive different amounts of sunlight. When a hemisphere leans toward the Sun, it experiences summer. The opposite hemisphere leans away and experiences winter.

The intensity of sunlight changes based on the angle at which it hits the Earth. During summer, the Sun is higher in the sky. This increases the solar flux, which is the amount of solar energy reaching a surface. In winter, the Sun's rays fall at a shallow angle. This causes the light to spread over a larger area. Consequently, the light is more indirect and has lower intensity. This change in light density and daylight hours accounts for most seasonal climate variations.

There are two ways to measure seasons: astronomically and meteorologically. Astronomically, a season is the time between an equinox and a solstice. An equinox occurs when the Sun is directly overhead at the Equator. During an equinox, day and night are equally divided between the hemispheres. A solstice marks the maximum or minimum amount of daylight. Meteorologically, seasons are defined as quarters of the annual temperature cycle. These meteorological seasons are centered on characteristic temperatures. They actually trail behind the equinoxes and solstices due to seasonal lag.

Seasonal lag is a phenomenon where the warmest months occur after the summer solstice. This happens because oceans take time to absorb and release heat. In the Northern Hemisphere, the warmest months are usually June, July, and August. In the Southern Hemisphere, the warmest months are December, January, and February. This lag explains why the peak temperature does not align perfectly with the peak sunlight. The thermal absorption of large bodies of water creates this delay in the temperature cycle.

Humanity has tracked these cycles for thousands of years. Ancient Egyptians defined seasons by the flooding of the Nile. They used three seasons: flood, growth, and low water. In India, six seasons called Ritu are used for agriculture and trade.

Even in Roman times, people used a four-season model. The writer Varro described specific dates for the start of each season. These historical definitions were vital for agrarian societies. They relied on seasonal changes to know when to plant and harvest crops.

While the tilt is the main cause, Earth's elliptical orbit also plays a small role. Earth reaches perihelion, its closest point to the Sun, in January. It reaches aphelion, its farthest point, in July. This creates a 7% variation in solar intensity. However, this effect is small and often opposes the temperature trends in the Northern Hemisphere. The Northern Hemisphere has more land, which warms more quickly than the sea. In contrast, the Southern Hemisphere has more water, which helps moderate its seasons.