The summer solstice: When is it and what causes it?

Sun shining through the stone arrangement at Stonehenge, UK.
Summer solstice marks the start of astronomical summer and is celebrated around the world. (Image credit: jessicaphoto via Getty Images )

The summer solstice marks the official start of astronomical summer and the longest day of the year. It occurs when one of Earth's poles is tilted toward the sun at its most extreme angle, and due to Earth's tilt this happens twice a year. In the Northern Hemisphere summer solstice falls in June (while the Southern Hemisphere experiences winter solstice), and in the Southern Hemisphere it falls in December (while the Northern Hemisphere experiences winter solstice).

The next summer solstice for the Northern Hemisphere will occur on June 21, 2023, and the next summer solstice for the Southern Hemisphere will occur on Dec. 21, 2022. 

The summer solstice and subsequent longest day of the year are celebrated by many cultures around the world with numerous traditions, holidays and festivals. From sunrise gatherings to midsummer festivals, summer solstice celebrations certainly blow the winter cobwebs away. 

Related: Summer solstice 2022 celebrated on Earth and in space (photos)

profile picture Daisy Dobrijevic
Daisy Dobrijevic

Daisy joined Space.com as a reference writer in February 2022, before then she was a staff writer for our sister publication All About Space magazine.  

What causes the summer solstice?

This infographic shows Earth during the June solstice and the December solstice. Hours of daylight and darkness for comparison. During the June solstice, the Arctic Circle receives 24 hours of daylight and but during the December solstice, the Arctic Circle receives 24 hours of darkness.   (Image credit: Peter Hermes Furian/Shutterstock)
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We have Earth's tilt to thank for the seasons, and without it both hemispheres would receive equal light throughout the year. 

As Earth orbits the sun, the axis of rotation of Earth is slightly tilted at 23.44°.1 according to the Royal Museums Greenwich (opens in new tab). This means that as Earth orbits the sun, the Northern Hemisphere is tilted towards the sun during one half of the year. During the other half of the year, the Southern Hemisphere tilts towards it. 

When the Northern or Southern Hemisphere is most tilted towards the sun, it experiences the summer solstice; when it is most tilted away, it experiences the winter solstice

The solstices also do not land on the same calendar day every year because the astronomical year is 365.25 days long. As such, the summer solstice for the Northern Hemisphere — also known as the June solstice — currently shifts between June 20, 21 and 22. The summer solstice does, however, occur at the same time for every country independently of which side of Earth is facing the sun. This means the exact moment of summer solstice can occur in the middle of the night for some people and the middle of the day for others. 

What is the meaning of solstice?

The word solstice is derived from the Latin word solstitium which translates to "sun stands still." This is due to the apparent movement of the sun to the north or south stops before changing direction, according to Dictionary.com (opens in new tab).

While the sun always rises in the east and sets in the west, it appears higher or lower in the sky throughout the year, depending on the season. Around the solstices, the sun reaches its apparent highest and lowest point in the sky. These correspond to midsummer and midwinter respectively, which are the turning points in the sun's journey. 

Once the sun reaches its zenith at the summer solstice, it will begin its journey toward the horizon, culminating in the winter solstice at its lowest point. In the weeks before these solstice turning points, the sun appears to move very little, earning it the name "sun standstill."

If you were to map the sun's midday position every day for a year, it would make a lopsided figure eight, called an analemma (opens in new tab). The point at which the curves of the figure eight intersect is the equinox, which is when day and night are roughly equal in length.

After plotting the sun's position for a year it makes a lopsided figure known as an analemma.   (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)
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When is the summer solstice 2023?

Summer solstice 2023 will occur on June 21 at 04:24 UTC for the Northern Hemisphere and on Dec. 21, 2022, for the Southern Hemisphere. To determine how many hours of daylight you'll receive during the summer solstice, you can use The Farmer's Almanac Sunrise and Sunset Calculator (opens in new tab)

Summer solstice celebrations

Midsummer celebrations in Blekinge, Sweden, with a maypole in the background.  (Image credit: Johner Images via Getty Images)
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Humans have been observing the sun's position in the sky for thousands of years, and monuments such as Stonehenge in England, Karnak (opens in new tab) in Egypt, and Chankillo (opens in new tab) in Peru stand as a testament to our fascination with our nearest star. Solstices have also influenced many traditions and celebrations around the world. 

At Stonehenge in the U.K., the sun rises behind the ancient entrance to a stone circle and "the sunlight is channeled into the center of the monument," the BBC (opens in new tab) reported. Researchers believe that solstices have been celebrated at Stonehenge for thousands of years. The stone circle is particularly important to pagans and druids.

According to some ancient Greek calendars, the summer solstice heralded the beginning of the new year and marked the one-month countdown to the start of the Olympic Games, according to St Neots Museum (opens in new tab) in the U.K. 

In Sweden, midsummer celebrations rooted in paganism are the highlight of the year for many. The weekend surrounding the solstice is filled with food, drink and plenty of singing, according to Lonely Planet (opens in new tab). Flower-wreath-wearing revelers take part in maypole and folk dances such as the traditional "Små grodorna". 

In the U.S., some Native American tribes living in the plains and The Rocky Mountains perform a Sun Dance (opens in new tab) to celebrate the summer solstice. In Fairbanks, Alaska, a baseball game known as the "Midnight Sun Game (opens in new tab)" traditionally starts at 10:30 p.m and takes a brief pause close to midnight for everyone to sing the Alaska Flag Song. 

In the Wiccan religion, people celebrate Yule (opens in new tab) at the winter solstice to herald the return of the sun and warmer months.

Additional resources

Explore the difference between the equinox and solstice with the UK Met Office (opens in new tab). Learn how to make your own solstice and equinox "suntrack" season model with NASA and the Stanford Solar Center (opens in new tab). Discover 11 interesting June solstice facts with Time and Date (opens in new tab)

Bibliography

Bland, A. (2012, December 20). The best places to see and celebrate the Winter Solstice. Smithsonian Magazine. Retrieved September 26, 2022, from https://www.smithsonianmag.com/travel/the-best-places-to-see-and-celebrate-the-winter-solstice-169694017/

Chankillo Archaeoastronomical Complex. World Monuments Fund. (2021, July 1). Retrieved September 26, 2022, from https://www.wmf.org/project/chankillo-archaeoastronomical-complex

Midnight Sun Game. Alaska Goldpanners of Fairbanks - Pointstreak Sites. Retrieved September 26, 2022, from http://goldpanners.pointstreaksites.com/view/goldpanners/june-21-2023-midnight-sun-game-tickets-go-on-sale-in-november-2022-stay-tuned

National Institutes of Health. Cheyenne Indians at a sun dance, by Edward S. Curtis, circa 1910. U.S. National Library of Medicine. Retrieved September 26, 2022, from https://www.nlm.nih.gov/nativevoices/exhibition/healing-ways/medicine-ways/key-role-of-ceremony/images/ob1410.html

Why do we celebrate the summer solstice? St Neots Museum. Retrieved September 26, 2022, from https://www.stneotsmuseum.org.uk/articles/why-do-we-celebrate-the-summer-solstice/

Salisbury, V. (2020, June 18). Top 8 summer solstice celebrations from around the World – Lonely Planet. Lonely Planet. Retrieved September 26, 2022, from https://www.lonelyplanet.com/articles/summer-solstice-celebrations

Sunrise and Sunset Times today: The old farmer's almanac. Almanac.com. Retrieved September 26, 2022, from https://www.almanac.com/astronomy/sun-rise-and-set

When is the summer solstice? Royal Museums Greenwich. Retrieved September 26, 2022, from https://www.rmg.co.uk/stories/topics/summer-solstice 

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Daisy Dobrijevic
Reference Writer

Daisy Dobrijevic joined Space.com in February 2022 as a reference writer having previously worked for our sister publication All About Space magazine as a staff writer. Before joining us, Daisy completed an editorial internship with the BBC Sky at Night Magazine and worked at the National Space Centre in Leicester, U.K., where she enjoyed communicating space science to the public. In 2021, Daisy completed a PhD in plant physiology and also holds a Master's in Environmental Science, she is currently based in Nottingham, U.K.