How Many Days Are In Summer On Average?

How many days are in summer on average? This depends somewhat on how you define summer, whether you are referring to the astronomical season of summer or the meteorological season. In terms of the meteorological summer season, there are 92 days in summer. The meteorological summer begins on June 1 and ends on August 31. Meanwhile, the astronomical summer begins on June 21st or 22nd and runs until the autumnal the equinox, coming to an end on September 21, 22nd, or 23rd.

Difference Between Meteorological Seasons and Astronomical Seasons

Climatologists and meteorologists will define seasons differently from how astronomers define seasons. There is a meteorological season as well as an astronomical season. Why is it that the astronomical seasons and meteorological seasons start and end at different times of the year? The difference is due to the fact that Meteorological seasons an astronomical seasons are defined differently, with meteorological seasons being based around the temperature cycle of the earth. Meanwhile, astronomical seasons are defined by how the position of the earth relative to the sun changes.

Astronomical Seasons

The Earth at various points in its seasonal orbit. Photo: Tauʻolunga via Wikimedia Commons, CC0

The astronomical season is based on the rotation of the earth around the sun. As the earth revolves around the sun, the tilt of the earth impacts how much sunlight different portions of the earth receive. The equinoxes referred to the two points of time every year where the sun moves directly above the equator, and there are (roughly) the same number of hours of daylight and nighttime for any given point on the Earth. After the equinox occurs the days continue to get longer or shorter until a solstice occurs. The summer solstice marks the point in time that there is the longest amount of daylight out of any day of the year, while the winter solstice refers to the point in the year when the days are the shortest. The winter solstice usually occurs around December 22, while the summer solstice usually happens around June 21. The spring equinox usually happens around March 21 while the autumnal equinox usually occurs around 22 September. The seasons are reversed for locations in the southern hemisphere.

Due to the fact that the earth takes approximately 365.24 days to travel around the sun, every four years another day is added to the calendar, making the year a leap year and February 29 a leap day. Leap years affect the exact date that the solstices and equinoxes occur. Other phenomenon that might affect when the solstice or equinoxes occur is the elliptical shape of Earth’s orbit. The astronomical seasons can vary about four days, being somewhere between 89 to 93 days.

Astronomical summer begins sometime between June 20 to June 22 and ends sometime between September 21 to September 23rd. Astronomical autumn begins sometime between September 21 to the 23rd and ends sometime between December 20 to December 23. Winter begins on the winter solstice which is sometime between December 20 to December 23 and ends on the spring equinox which occurs sometime between March 19-21. Finally, spring starts during the spring equinox from March 19 to the 21st of March and ends at the summer solstice which is somewhere around June 20 to June 22nd.

Meteorological Seasons

Climatologists and meteorologists divide the seasons into three months each, based on the Gregorian calendar and the annual temperature cycle of the earth. Meteorological seasons are what most people think of when they hear the word season, and their intuitions about them are largely correct. Winter is the coldest time of the year and it occurs over the months of December, and January, February. Meteorological Spring is a transition time between winter and summer, and it occurs of the months of March, April, and May. Summer is the hottest time of the year when the days on longest, and the meteorological summer occurs over the months of June, July, and August. Finally, meteorological fall is a transition time between the summer and the winter and it occurs of the months of September, October, November.

Because meteorological seasons are somewhat based on our civil calendar, they tend to be more consistent and astronomical seasons. The length of meteorological season may only range a day or two, with the winter of a non-leap year being exactly 90 days long and spring and summer being 92 days long. The reason that meteorological seasons are based so closely on the calendar is that it enables the calculation of seasonal statistics based off of monthly statistics. These statistics are important in operations like commerce and agriculture.

Meteorological spring begins with 1 March and ends on June 1 while summer runs from June 1 to September 1. Meteorological autumn starts September 1 and ends December 1, while meteorological winter runs from December 1 to March 1.

How Many Daylight Hours Are In Summer?

Photo: jill111 via Pixabay, CC0

Now that we’ve looked at the amount of days in the summer season, let’s look at the number of daylight hours in a summer season. During the summer months there is more daylight, but how many hours of daylight are in the average summer exactly?

Factors that influence the length of daylight include the elliptical orbit of the earth and the tilt of the earth. The tilt of the earth is what is primarily responsible for the variation in the amount of daylight over the seasons. The earth is tilted approximately 23.5° perpendicular to the path of its orbit, and while the earth completes an entire revolution around the sun over the course of the year the tilt of the earth is always pointed in the same direction towards the sun (the angle of the tilt varies). Because of this tilt, different parts of the earth get different amounts of sunlight during the summer even though they all experience more daylight in the summer (in that hemisphere). The imbalance between the amount of daylight and nighttime becomes more prominent as you move away from the equator to the polls.

At the Arctic Circle, which is around 66.5° North latitude, there is essentially sunlight 24 hours of the day for a few weeks during the beginning of summer, around the summer solstice. The reason this occurs is that the axis of the earth is tilted so that the Arctic circle is pointed directly towards the sun at this time. These small regions of the planet won’t completely rotate out of the sun’s rays until a few weeks have passed. However, during the summer solstice everywhere else on earth will also receive the maximum amount of daylight hours possible.

By the end of the summer, the axis of the earth is neither pointed towards the sun nor will it be pointed away from the sun. This occurs on the fall equinox, approximately September 21 September 22 in the northern hemisphere. Because the earth’s axis isn’t tilted at all relative to the sun, everywhere on the planet should receive approximately 12 hours of darkness and 12 hours of daylight. The same thing happens during the spring equinox after the amount of sunlight is increased from the shortened hours during the winter.

There are various websites that will allow you to calculate how many hours of daylight a specific location will receive a certain date on every day of a given year. You can enter a location such as, Portland, Oregon and finds that at the time of the summer solstice the city receives 15 hours and 41 minutes of daylight. Meanwhile, Tampa, Florida will receive about 13 hours and 53 minutes of daylight on June 30th of 2019.

How Many Days Of Summer Vacation?

Photo: MaeM via Pixabay, CC0

There’s another context in which somewhat might ask, “How many days are in a summer on average”. Here, they might be using the word “summer” to refer to summer vacation – the period of time that school children are off of school over the summer.

The average number of days in summer vacation, in the United States, can vary widely between school districts. Summer vacation can be anywhere from 42 to 98 days or 6 to 14 weeks long. According to the National Center for Education Statistics, the average instructional school year length is 180.4 days or 36 five-day weeks. This means that the average school year runs for about 252 days, meaning that if the earliest possible candidates and the latest possible school start date are taken into account, there are about 103 to 104 days of summer vacation.

Obviously, the length of summer vacation varies based off of the region of the United States. The start and end dates for summer vacation also vary depending on geographical regions. Most schools found in the northern part of the United States start summer vacation in early June with school starting again in early September. Meanwhile, southern states frequently have the summer vacation begin in late May with school starting again in late August. Almost all schools give their students a few days off during November for the Thanksgiving holiday as well as between 1 to 2 weeks off during December and into January for the Christmas break. Spring break and modification fall holidays are also observed.

About The Author

Daniel Nelson

Daniel obtained his BS and is pursuing a Master's degree in the science of Human-Computer Interaction. He hopes to work on projects which bridge the sciences and humanities. His background in education and training is diverse including education in computer science, communication theory, psychology, and philosophy. He aims to create content that educates, persuades, entertains and inspires.

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