Science of the Summer Solstice: Start of Summer


Solstice comes from the Latin word solstitium, meaning “Sun, standing still.” The Summer Solstice occurs on June 20 at 20:51 UTC, Coordinated Universal Time, Zulu Time, or roughly Greenwich Mean Time. Greenwich, England, is the prime meridian — the zero point for longitude lines.

Why is UTC the abbreviation for Coordinated Universal Time?

The acronym came about as a compromise between English and French speakers: Coordinated Universal Time would normally be abbreviated as CUT, and the French name Temps Universel Coordonné would be TUC.


Summer Time and the Summer Solstice

This is also known as the Northern Solstice because the Sun is positioned directly above the Tropic of Cancer in the Northern Hemisphere.

  • This time of year is known as Midsummer, though the official Midsummer Day is actually celebrated on June 24, thanks to differences between the Julian and Gregorian calendars.


Does Summer Start on the Summer Solstice?

Short answer: Yes.

Longer Answer: And… 

Have you notice how some people declare the “unofficial” start of Summer following Memorial Day at the end of May? Despite the fact that it used to mark the end of the school year, there’s actually some science to it.

While the Solstice is the beginning of the astronomical Summer, June 1st is the beginning of the meteorological Summer.


Meterological Seasons


What is meteorological Summer, and how does it differ?

  • Astronomical seasons are based on the position of Earth in relation to the Sun, which I’ll explain below.
  • Meteorological seasons are based on the annual temperature cycle.

Astronomy is an ancient science, and modern meteorology is more recent. Significant progress was not seen until the 18th century. It has risen in popularity due to climate studies. Meteorological observation and forecasting led to the creation of these meteorological seasons, which are more closely tied to our monthly civil calendar than the astronomical seasons.

According to the National Centers for Environmental Information, each season ranges from 90 days for Winter of a non-leap year to 92 days for Spring and Summer.




Meteorologists and climatologists divide the seasons into groupings of three months based on the annual temperature cycle and our calendar. Meteorological Spring in the Northern Hemisphere includes March, April, and May; meteorological Summer includes June, July, and August; meteorological Fall includes September, October, and November; and meteorological Winter includes December, January, and February.


The Solstice in Summer Solstice

Solstice2Earth enjoys different seasons because it is tilted 23 degrees and 27 minutes off the perpendicular to the plane of orbit. This means that the Earth revolves like a tilted spinning top. The Summer Solstice is the longest day of sunlight, as the Sun is at its highest arc in the sky, at least in the Northern Hemisphere.

The farther north one is from the Equator, the more pronounced this is in Summer. However, as the Earth continues its orbit, the hemisphere angled closest to the sun changes, and the seasons are reversed.

In the Northern Hemisphere, the Sun appears at its highest point in the sky, and its noontime elevation seems to be the same for several days before and after the Solstice. So, it looks like the Sun is “standing still” until following the Summer Solstice when the days begin to grow shorter and the nights longer.


Summer Solstice Know-It-All Facts to impress your friends and neighbors:

  • The Summer Solstice is not the longest day of the year, only the one with the most daylight. The longest day (no relation to the movie) is in November when we “fall back” to Daylight Saving Time and pick up an extra hour in the day, making it 25 hours long.
  • The Earth is actually farthest from the Sun on the Summer Solstice
  • Your noontime shadow is the shortest of the year on the Summer Solstice
  • Fairbanks, Alaska, gets almost 24 hours of sunlight on the Summer Solstice. They routinely have an annual midnight baseball game.


Bill Petro, your friendly neighborhood historian

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About billpetro

Bill Petro writes articles on history, technology, pop culture, and travel. He has been a technology sales enablement executive with extensive experience in Cloud Computing, Automation, Data Center, Information Storage, Big Data/Analytics, Mobile, and Social technologies.

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