Summer solstice 2021: When is it and what is it?

The celebation, also known as the longest day of the year, marks the return of brighter evenings.

Here is all you need to know:

What is Summer Solstice?

The Solstice is the beginning of the astronomical summer in the Northern Hemisphere.

It ends with the autumn equinox on September 22.

Solstice marks almost equal duration of day and night as the Sun crosses the Line of Equator and moves over the Northern Hemisphere.

On June solstice, the Earth is positioned is a way that the North Pole tilts towards the Sun. 

Crowds cheer the rise of the sun at Stonehenge

When is the longest day of the year?

In the northern hemisphere, the summer solstice, or longest day of the year, takes place between June 20 and 22 each year. 

This year it falls on Monday, June 21 - when the UK will enjoy 16 hours and 38 minutes of daylight.

The sun will rise at 4.52am and set at 9.26pm.

Summer Solstice celebrations

A number of ancient celebrations are associated with the June Solstice.

People used the day to organize calendars and farmers marked the day with sowing or harvesting of crops.

Many historians say, Stonehenge, a prehistoric monument in England, is an evidence of humans using June Solstice as a way of setting the time of the year.

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Even now, tourists and locals visit Stonehenge to watch the sunrise on Summer Solstice.

According to the timeanddate.com, "In ancient China, the Summer Solstice was observed by a ceremony to celebrate the Earth, femininity, and the 'yin' forces. It complemented the Winter Solstice that celebrated the heavens, masculinity and 'yang' forces."

In Sweden, Denmark, Norway and Finland, Summer Solstice is a time of midsummer night festivities.

This is the time when countries near the Arctic enjoy the Midnight Sun.

A woman twirls a hula-hoop as the sun rises at Stonehenge Picture: PA

People dance around the Maypoles and bonfires.

Homes are lit up and decorated with violets and vanilla flowers.

What happens during the summer solstice?

There are two solstices each year - one in the winter and one in the summer.

The summer solstice occurs when the tilt of Earth's axis is most inclined towards the sun and is directly above the Tropic of Cancer.

The event signals the moment the sun's path stops moving northward in the sky, and the start of days becoming steadily shorter as the slow march towards winter begins. 

However, we won't notice the days becoming shorter for a while. 

The shortest day of the year isn't until Monday, December 21, known as the winter solstice; it lasts for 7 hours and 50 minutes in Britain, which is 8 hours, 48 minutes shorter than the June solstice.

A woman wears a colourful head-dress at Stonehenge Picture: PA

At the winter solstice, the Earth's axis is tilted furthest away from the sun directly over the Tropic of Capricorn bringing only a few hours of daylight.

In the southern hemisphere the dates of the two solstices are reversed. The winter solstice occurs on the same day in June and the summer solstice the same day in December.

The term "solstice" derives from the Latin word "solstitium", meaning "sun standing still". 

Astrologers say the sun seems to "stand still" at the point on the horizon where it appears to rise and set, before moving off in the reverse direction.