21 June is the summer solstice, or longest day, in the northern hemisphere and the winter solstice, or shortest day, in the southern hemisphere
By Abigail Beall
21 June 2023
People throng Glastonbury Tor in Somerset, UK, during the summer solstice
Graham Hunt/Alamy
Today, 21 June, is the June solstice. Also known as the summer solstice in the northern hemisphere and the winter solstice in the southern hemisphere, the June solstice marks the time at which the sun is directly above the Tropic of Cancer.
This is the furthest north the sun reaches throughout the year, and it marks the northern hemisphere’s longest day of the year – and the shortest day in the southern hemisphere.
When is the June solstice 2023?
The solstice isn’t technically a day, but a time. It usually happens on 21 or 22 June, and this year it is on 21 June at 3.57pm BST.
Advertisement
What causes the June solstice?
Earth’s axis of rotation is tilted by 23.5 degrees with respect to the plane it orbits around the sun. This is why we have seasons – during summer in the northern hemisphere, the north pole is tilted towards the sun, and during summer in the southern hemisphere, the south pole is tilted towards the sun.
The June solstice marks the moment during the year when the north pole reaches its maximum tilt towards the sun.
Read more:
A stargazer's guide to the equinox and how Earth moves around the sun