Home > Calendar > Defining Seasons

Seasons: Meteorological and Astronomical

There are meteorological and astronomical seasons, both marked by specific weather conditions, temperatures, or length of the days.

Illustration image

The four seasons.

The four seasons are spring, summer, fall (autumn) and winter.


Earth spins around the Sun at an angle, which is why we have different seasons.

Most modern day calendars around the world reflect this and divide the year into 4 seasons: spring, summer, fall (autumn), and winter.

The dates of when these seasons begin and end, vary depending on who you ask.

Opposite Sides and Seasons

People in the Southern Hemisphere, like Australia and New Zealand for example, consider September 1 as the beginning of spring.

The Irish, on the other hand, begin spring on February 1 when they celebrate St Brigid's Day. Some cultures, especially those in South Asia have calendars that divide the year into 6 seasons, instead of the 4 that most of us are familiar with.

Astronomical Seasons

Astronomers and scientists use the dates of equinoxes and solstices to mark the beginning and end of seasons in a year.

In the Northern Hemisphere, the four astronomical seasons are:

Because the dates of the equinoxes and solstices can change, the length of astronomical seasons within a year and between years can vary.

Equinoxes and solstices dates worldwide

Northern Meteorological Seasons

To be consistent and to make weather forecasting easier, meteorologists divide the year into 4 meteorological seasons of 3 months each:

  • Spring - from March 1 to May 31;
  • Summer - from June 1 to August 31;
  • Fall (autumn) - from September 1 to November 30; and,
  • Winter - from December 1 to February 28 (February 29 in a leap year).

Opposite Sides – Opposite Seasons

Seasons in the Southern Hemisphere are opposite to those in the Northern Hemisphere. For example, under the definition of astronomical seasons, the June Solstice marks the start of summer in the Northern Hemisphere, but is the start of winter in the Southern Hemisphere. The same rule applies for the other 3 seasons.

The meteorological seasons in the Southern Hemisphere are also opposite to those in the Northern Hemisphere:

  • Fall (autumn) - starts March 1 and ends May 31;
  • Winter - starts June 1 and ends August 31;
  • Spring - starts September 1 and ends November 30; and,
  • Summer - starts December 1 and ends February 28 (February 29 in a Leap Year).
Equinox and solstice illustration.
Equinoxes and solstices mark the start and end dates of astronomical seasons.
Equinoxes and solstices mark the start and end dates of astronomical seasons.

Earth's Rotational Axis

Seasons occur because of the tilt of the Earth's rotational axis, which is about 23.4 degrees. Around the June Solstice, the Northern Hemisphere is titled toward the Sun. This causes summer there. The Southern Hemisphere, on the other hand, is tilted away from the sun and therefore, experiences winter. The opposite occurs around the December Solstice when the Southern Hemisphere is tilted toward the Sun, while the Northern Hemisphere is tilted away.

Topics: Astronomy, Seasons, March, June, September, December

In This Article


The Science of Seasons

  1. Meteorological vs. Astronomical Seasons
  2. Perihelion, Aphelion & Solstice

What Causes Seasons on Earth?

Astronomical Season Calculator

Winter & Summer Solstices

  1. What is the June Solstice?
  2. Facts about June Solstice
  3. What is the December Solstice?
  4. Facts about December Solstice
  5. When is the Summer Solstice?
  6. When is the Winter Solstice?
  7. June Solstice Celebrations
  8. December Solstice Celebrations
  9. What Causes Seasons?

Equinox & Solstice Worldwide

Sunrise & Sunset Times

Vernal & Autumnal Equinox

  1. Vernal (Spring) Equinox
  2. Autumnal (Fall) Equinox
  3. March Equinox
  4. 10 Facts: March Equinox
  5. March Equinox Celebrations
  6. September Equinox
  7. 10 Facts: September Equinox
  8. September Equinox Celebrations
  9. Nearly Equal Night & Day

Equinox & Solstice Worldwide

You might also like

Equinox and solstice illustration.

When is Fall Equinox?

The fall (autumnal) equinox in the Northern Hemisphere is in September. In the Southern Hemisphere, it's in March. more

Equinox and solstice illustration.

When is Spring Equinox?

The Vernal (Spring) Equinox in the Northern Hemisphere is in March. In the Southern Hemisphere, it's in September. more