Seasons: Meteorological and Astronomical
There are meteorological and astronomical seasons, both marked by specific weather conditions, temperatures, or length of the days.
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
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.
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:
- Spring - March Equinox to June Solstice;
- Summer - June Solstice to September Equinox;
- Fall (autumn) - September Equinox to December Solstice; and,
- Winter - December Solstice to March Equinox.
Because the dates of the equinoxes and solstices can change, the length of astronomical seasons within a year and between years can vary.
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).
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 tilted 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.
In This Article
- Opposite Sides and Seasons
- Astronomical Seasons
- Meteorological Seasons
- Opposite Seasons
- Earth's Rotational Axis
The Science of Seasons
- What Causes Seasons?
- Earth's Axis Is Tilted
- Meteorological vs. Astronomical Seasons
- What Is a Solar Analemma?
Winter & Summer Solstices
- What is the June Solstice?
- Facts about June Solstice
- What is the December Solstice?
- Facts about December Solstice
- When is the Summer Solstice?
- When is the Winter Solstice?
- June Solstice Celebrations
- December Solstice Celebrations
Vernal & Autumnal Equinox
- Vernal (Spring) Equinox
- Autumnal (Fall) Equinox
- March Equinox
- 10 Facts: March Equinox
- March Equinox Celebrations
- September Equinox
- 10 Facts: September Equinox
- September Equinox Celebrations
- Nearly Equal Night & Day