Summer is officially here (for some of us, at least). Marked by the summer solstice 2024, today the Northern Hemisphere will have more hours of sunlight than any other as the astronomical season begins.
Today has held significance in the hearts and minds of people spanning thousands of years. Whether celebrating religious ceremonies or simply firing up the BBQ for the first time, the longest day of the year is a cause for celebration.
But if you’re not sure what it is, or why it’s important to sites like the famous Stonehenge, we’ve got you covered.
When is the summer solstice 2024?
In 2024, the summer solstice will occur on Thursday 20 June at 9.51pm BST (4:50 pm EDT New York, 1:50pm PDT Los Angeles). While many people mark the whole day's importance, the solstice actually occurs at an exact moment – so make sure you don’t miss it.
The event occurs on the first day of the astronomical summer season, marking the moment when the northern hemisphere is directly facing the Sun.
This day is also the longest of the year, featuring the greatest number of daylight hours in 2024. In the UK and the US, you can expect at least 16 hours of daylight.
This is one of the two solstices each year, with the second one happening in December. The summer solstice always falls between June 20 and 22, and this year, it arrives one day earlier than in 2023.
When are sunrise and sunset on the summer solstice?
On Thursday 20 June, sunrise in London, UK, will occur at 4:43am BST, while the sunset will come at 9:21pm BST. Depending on where you are in the UK, the time will vary by a couple of minutes or so.
For those of you in the US, times vary a little more depending on where you are in the country:
- New York City summer solstice sunrise time: 5:25am EDT.
- New York City summer solstice sunset time: 8:31pm EDT.
- Austin, Texas, summer solstice sunrise time: 6:30am CDT.
- Austin, Texas, summer solstice sunset time: 8:36pm CDT.
- Los Angeles summer solstice sunrise time: 5:42am PDT.
- Los Angeles summer solstice sunset time: 8:08pm PDT.
The astute amongst you may have noticed that although today marks the longest day of the year, it’s not the earliest sunrise, nor the latest sunset.
The precise date of the earliest sunrise (and earliest sunset) changes depending on the latitude.
At a latitude of 40 degrees north – which includes places like Philadelphia in Pennsylvania, the Mediterranean Sea, northern Japan and Bejing in China – the earliest sunrise of the year occurred around June 14.
Similarly, at this latitude, the latest sunset of the year happens around June 27.
"This slight difference is caused by the Earth orbiting the Sun not in a circle, but in a slight ellipse,” Dr Darren Baskill, an astrophotographer and astronomy lecturer at the University of Sussex, tells BBC Science Focus.
Read more:
- When does summer start 2024 and when is the longest day?
- Summer solstice: five big questions
- Is there more oxygen in the air in the summer?
What is the summer solstice?
The reason for the exact nature of the summer solstice is that it occurs at the moment when the Sun reaches its highest point in the sky, which is when the Northern Hemisphere is most titled toward the sun.
In other words, this is the moment when the Sun’s rays strike the northern half of the planet most directly.
"The summer solstice occurs for the Northern Hemisphere when the Earth moves into such a position that its North Pole is pointing in the direction of the Sun, making the Sun high in the sky," says Baskill.
"At the same time, the South Pole of the Earth is pointing away from the Sun, and so the Southern Hemisphere has their winter solstice on the same day."
The Earth's axis is tilted about 24 degrees relative to its orbit around the Sun. On June 20, the Northern Hemisphere is tilted closest to the Sun, while the Southern Hemisphere is tilted farthest away, leading to opposite seasons in the two hemispheres.
As a result, when the Northern Hemisphere experiences the summer solstice, the Southern Hemisphere simultaneously experiences its winter solstice, and vice versa.
This seasonal difference is due to the axial tilt rather than the Earth's distance from the Sun.
In fact, Earth reaches its closest point to the Sun, called perihelion, in January, and its farthest point, known as aphelion, in July.
Despite the summer solstice marking the longest day of the year, it is not typically the hottest day (apologies to those currently in the throes of a heatwave in the US). The peak temperatures usually occur in July or August because the oceans and land masses continue to release the heat they have absorbed from the prolonged daylight.
Why is the Earth tilted?
You might think it would make sense for the Earth’s poles to match up the plane of its orbit around the Sun. You’d probably be right, but alas, the Universe is not a perfect place.
"Go back 4.5 billion years, and our infant Solar System was a violent place, with vast numbers of large asteroids hitting the young planets," says Baskill.
"One particularly large collision between the Earth and an object half its size led to the creation of the Moon – that's the only way we know for such a relatively large moon to end up in such an orbit around the Earth.
"Today's tilt of the Earth is caused by the sum of all of the impacts that were big enough to affect the tilt, including the impact that formed the Moon."
This severe tilt means that if you’re particularly far north around this time of year, the Sun doesn’t even set – a permanent day sets over the Arctic regions of our planet.
How is the summer solstice marked around the world?
From Midsummer in Sweden (marked slightly after the solstice this year on June 22 and now immortalised by the terrifying 2019 film, Midsommar), to mountaintop bonfires in the Austrian Tirol, the summer solstice is marked by people and cultures the world over.
The most famous of all, however, is the event taking place at Stonehenge, in Wiltshire, England.
The mysterious stone circle was built by prehistoric people some 5,000 years ago – before the invention of the wheel had reached Britain’s shores. While little is known about its designers, they were clearly in touch with the cosmos with remarkable precision.
On the morning of the summer solstice, the sun rises on the northeastern horizon and shines directly through the outer circle onto an altar stone at its centre.
Today, hundreds of people still gather at the monument to usher in the astronomical summer season. In fact, the summer solstice is the only day that the site has free access to tourists, allowing revellers to come and experience this ancient and sacred event.
What’s the difference between an equinox and a solstice?
Equinoxes and solstices are both key points in our year, but they mark different seasonal shifts.
An equinox (from the Latin for "equal night") brings about roughly equal day and night lengths.
We have two equinoxes a year, around March 20th (vernal equinox) and September 22nd (autumnal equinox), marking the start of spring and autumn respectively.
Solstices (from the Latin for "sun standing still") on the other hand, are all about sunlight.
The summer solstice, around June 21st, brings the longest day of the year in the Northern Hemisphere, while the winter solstice, around December 21st, is the shortest. So, solstices mark the peak of summer and the depths of winter.
Do any other planets have solstices?
Before you go thinking that we’re special, every planet in the Solar System has at least some axial tilt, and therefore every planet has solstices.
That said, Earth’s tilt is pretty pronounced. Venus and Jupiter, for example, are tilted by only around 3 degrees, while Mercury is a mere 0.03 degrees out of kilter.
Uranus, meanwhile, is seriously askew. Its poles are a whopping 97.8 degrees from vertical, meaning they point directly at the Sun at times.
Mars’ axis is similarly tilted to ours at 25.2 degrees, yet its seasons last twice as long and our less easy to define due to its elliptical orbit.
Dates and times of future summer solstices, BST
- 2025: 21 June, 3:42am
- 2026: 21 June, 9:24am
- 2027: 21 June, 3:10pm
- 2028: 20 June, 9:01pm
- 2029: 21 June, 2:48am
- 2030: 21 June, 8:31am
About our expert
Darren Baskill is an outreach officer and lecturer in the Department of Physics and Astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.
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