The Earth’s axis is slightly tilted in relation to its orbit around the Sun. This is why we have seasons.
How exactly do seasons work?
In most cultures, including all western countries, the year is commonly divided into four seasons:
- Fall or Autumn
Since the year has 12 months, each season lasts about three months. However, the dates when the seasons begin and end vary depending on whom you ask. Two methods are most commonly used to define the dates of the seasons: the astronomical definition and the meteorological definition.
The astronomical definition uses the dates of equinoxes and solstices to mark the beginning and end of the seasons:
- Spring begins on the spring equinox;
- Summer begins on the summer solstice;
- Fall (autumn) begins on the fall equinox; and
- Winter begins on the winter solstice.
The beginning of each season marks the end of the last.
Because the timings of the equinoxes and solstices change each year, the length of astronomical seasons within a year and between years also varies.
According to the meteorological definition, the seasons begin on the first day of the months that include the equinoxes and solstices. In the Northern Hemisphere, for example,
- spring runs from March 1 to May 31;
- summer runs from June 1 to August 31;
- fall (autumn) runs from September 1 to November 30; and
- Winter runs from December 1 to February 28 (February 29 in a leap year).
The United States has nine climate regions -and the four seasons – spring, summer, winter, and fall and their onsets – and how they present – vary dramatically between those nine climate regions.
Enjoy Seasons in America!