Summer solstice 2023: When is it and what causes the year’s longest day?

Here’s when the summer solstice takes place this year, what it represents, and why Stonehenge is so important.

By Toby Saunders

Published: Monday, 12 June 2023 at 12:00 am

Get out those sandals, BBQs, and sun hats because the summer is finally here! Whether you like it or not, we’re now halfway through 2023 and the summer solstice marks the astronomical start of the season.

More specifically, the summer solstice signals an important moment in the calendar for many and it’s no different in 2023. But when is it exactly? What does it mean? We’ve got these answers and more below.

Read on to find out how the event is marked around the world, what the difference between an equinox and a solstice is, and to see if any other planets have solstices or not.

When is the summer solstice in 2023?

The summer solstice in 2023 will take place on Wednesday 21 June at precisely 3:58pm BST in the UK and 10:58am ET / 7:58am PT. Contrary to popular belief, the solstice is an exact moment and not the entire day.

The event takes place on the first day of the astronomical summer season and marks the exact point the northern hemisphere is pointing directly towards the Sun.

It also marks the longest day of the year, with the highest number of daylight hours seen in a single day in 2023. Expect at least 16 hours of daylight in the UK and in the US.

This is the first of two solstices during the year, with the second taking place in December. The summer solstice will always take place between 20-22 June. It just so happens to be falling on the same day as in 2022 this time around.

What is the summer solstice?

The summer solstice takes place at the exact moment the Sun reaches its highest point in the sky, which is when the northern hemisphere is tilted most towards the Sun. Essentially, it marks the point when the Sun’s rays hit this part of the Earth most directly.

The Earth’s axis has a tilt of around 23.4 degrees, relative to its orbit around the Sun. On 21 June, the northern hemisphere is tilted at its closest point towards the sun and the southern hemisphere is tilted its furthest away from the Sun, which is why the northern and southern hemispheres have opposite seasons to one another.

This means that the southern hemisphere will be celebrating its winter solstice at the same time as our summer event and vice versa.

Because it is related to tilt and not orbit distance, the Earth is actually closest to the Sun (the perihelion) in January and furthest from it (the aphelion) in July.

The summer solstice is not necessarily the hottest day of the year. Usually, the hottest day of the year is in July or August. This is because oceans and land masses release the heat absorbed from the longer days back into the atmosphere.

How is the summer solstice marked around the world?

The summer solstice is marked around the world by different groups and cultures, but the most famous event arguably takes place at Stonehenge in the UK.

While many mysteries remain about the ancient stone circle, we do know that the monument is structured to mark the position of the rising sun at the solstices (whether that was its original intention or not). As such, 21 June 2023 marks the only day the site has free (managed) open access for tourists and those looking to take in the special and sacred event.