Autumn, usually called fall
in North America, is one of the four seasons that make up the year. It is the intervening period between the warmest time of the year, summer
, and the coldest time of the year, winter
Astronomical autumn vs. meteorological autumn
There are various ways to define the start and end dates of autumn. The two most commonly used ones are based on the astronomical calendar and the meteorological calendar. Astronomical and meteorological autumn start and end on different dates.
In the astronomical calendar the start and end dates of autumn are based on the changing position of Earth in relation to the sun and the resulting solar events of equinoxes and solstices. In the Northern Hemisphere summer ends and autumn starts at the moment of the September equinox
, which occurs every year between September 21 and 24. Autumn ends and winter starts at the moment of the December solstice
, which occurs every year between December 20 and December 23. In the Southern Hemisphere autumn lasts from the March equinox
(March 19 to 21) to the June solstice
(June 20 to 22).
The start and end dates for autumn given on this page are the dates of astronomical autumn in the Northern Hemisphere and are based on Coordinated Universal Time (UTC), which for practical purposes is equivalent to Greenwich Mean Time (GMT - the time zone of the United Kingdom). While autumn starts and ends at the same moment in time all over the Northern Hemisphere, the date and local time differ from place to place depending on the year and a location's time zone. For locations that are ahead of UTC (further east) it may fall on the day after, and for locations that are behind UTC (further west) it may fall on the day before. To find out the exact date and time of autumn 2021 in your area use this seasons calculator
Meteorologists, on the other hand, define seasons based on climatic conditions and the annual temperature cycle. It is important for them to be able to compare the same period of time in different years. The length of the astronomical seasons varies between 89 and 93 days, while the length of the meteorological seasons is less variable and is fixed at 90 days for winter in a non-leap year (91 days in a leap year
), 92 days for spring and summer, and 91 days for autumn. While the exact definition of a season's timing and length can differ in different areas based on local conditions, in most of the Northern Hemisphere meteorological autumn is generally defined as the three months of September, October and November, with the season starting on September 1 and ending on November 30.
There is no "official rule" which definition of autumn to use, and different countries adhere to different conventions. Most of North America and Europe use astronomical autumn, while Australia and New Zealand use meteorological autumn (however, as these countries are in the Southern Hemisphere, the seasons are opposed and autumn there lasts from March to May). In other cultures, eg. in the traditional Chinese calendar and in Celtic traditions, the September equinox is considered to be roughly the middle of autumn.
Comparison table: meteorological spring vs. astronomical spring
Dates shown apply to the Northern Hemisphere and are based on UTC (GMT)
2021 calendar as templates for
Word, Excel and PDF
A selection of calendar templates for 2021 in landscape and portrait orientation and with US federal holidays, suitable for a variety of applications.