I can usually guarantee that upon returning to college for a new academic year, and within the first few days of September, I will hear some variation of the following statements:

  1. Autumn is here…..but
  2. We normally get a few nice days in September.

There is a simple reason for this…it’s still summer. This is true in the UK at least, exact dates will vary depending on where you are in the world, particularly whether you are in the northern or southern hemisphere. It may seem strange that we can talk about summer going into late September when the last sunsets of the summer are around 7.15 pm in my part of the world, yet here we are.

There are two views of when summer (in the UK) ends:

  1. Meteorological summer. The last day of summer is August 31st, and the 1st day of summer is September 1st.
  2. Astronomical summer. The last day of summer is around September 22nd or 23rd, starting around June 20th or 21st.

Meteorological summer depends on seeing summer as the three months of June, July & August.  Autumn therefore is September, October & November. Winter is December, January & February. Spring is March, April & May. It is the definition of summer that is preferred by weather forecasters. It is a convenient way of defining the months and is helpful for meteorologists when it comes to comparing data and generating statistics, such as the hottest/coldest day of a particular season. It is useful, therefore, for comparing year-on-year weather patterns, if a little simplistic.

Astronomical summer is based on solstices, equinoxes and the Earth’s relationship to, and movement around the Sun. The two solstices of the year are around June 21st and December 21st, the times when the Sun’s path is either farthest north or south from the Equator. The two equinoxes of the year, when the sun crosses the equator, are around March 21st and September 21st. Astronomical summer therefore begins at the summer solstice and ends at the autumn equinox.

Does any of this matter? Not really, and sometimes the main use of this information can be for fascinating or boring people at parties, depending on how wisely one chooses one’s friends and acquaintances.


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