What Causes the Four Seasons: Spring, Summer, Fall, and Winter?

The advent of a new season brings many changes. Here in the Northern Hemisphere, it’s officially autumn. The leaves are turning from green to yellow, orange, and red hues. The air feels crisp, and the days are shorter.

As we enjoy the beginning of a new season, have you ever wondered why seasons exist?

The four seasons exist thanks to the Earth’s axis. In this post, we’ll break down why seasons exist, and how they’re different in the Northern and Southern hemispheres.

Why Seasons Exist

The Earth tilts 23.5 degrees on its axis relative to the orbital plane: the invisible, flat disc where objects in the solar system orbit the sun. As Earth orbits the sun every 365 ¼ days, the axis is always pointing in the same direction.

The Northern and Southern Hemispheres tilt toward the sun during different months, which is why we have different seasons at different times in the United States than in Australia. For example, in June, the Northern Hemisphere is tilted toward the sun, meaning sun rays hit that portion of Earth for a greater part of the day, resulting in more daylight hours and warmer weather.

Let’s break down the seasons for each hemisphere.

The Northern Hemisphere

In the Northern Hemisphere, winter begins on either Dec. 21 or 22, marking the winter solstice, which is the day of the year with the shortest daylight period. On the other hand, summer begins on either June 20 or 22, marking the summer solstice, which is the day of the year with the most daylight hours.

Spring and fall begin on equinoxes, which are days that have an equal amount of daylight and darkness. The vernal, or spring, equinox, falls on March 20 or 21, while the autumnal equinox falls on Sept. 22 or 23.

The Southern Hemisphere

What we just discussed about the Northern Hemisphere is the opposite in the Southern Hemisphere. Remember, the seasons are different because the hemispheres face the sun at other times during the year. In countries like Australia and Argentina, winter begins in June while summer is in December.

2020 Seasons:

• Spring begins with the Vernal Equinox, Thursday, March 19, 2020, 11:50 p.m.
• Summer begins with the Summer Solstice, Saturday, June 20, 2020, 5:44 p.m.
• Fall begins with the Autumnal Equinox, Tuesday, September 22, 2020, 9:31 a.m.
• Winter begins with the Winter Solstice, Monday, December 21, 2020, 5:02 a.m.

Source: Farmer’s Almanac

In summary, seasons exist because of Earth’s rotational axis. Seasons are different in the Northern and Southern Hemispheres because they face the sun at other times during the year. While the Northern Hemisphere enjoys snowstorms in December, the Southern Hemisphere is soaking up the sun.