In astronomical terms, summer begins Wednesday with the arrival of the summer solstice, which marks the longest day of the year for everyone north of the equator.
This year, the summer solstice falls at exactly 10:57 a.m. EDT, when the sun is directly over the Tropic of Cancer. South of the equator, the same time marks the astronomical start of winter.
On two moments each year, Earth’s axis tilts the most toward the sun. The hemisphere that tilts closer to the sun experiences its longest day, whereas the hemisphere that tilts away from the sun experiences its longest night.
The summer solstice takes place between June 20 and 22 each year. By meteorological standards, summer for the Northern Hemisphere begins on June 1.
This year, the winter solstice will take place on December 21, marking the shortest day of the year for the Northern Hemisphere.
On the summer solstice, the amount of sunlight people experience depends on how far north they are. The northernmost latitudes experience a full 24 hours of sunlight. By comparison, most of the United States will experience between 14 and 16 hours of sunlight.
The word solstice comes from the Latin words sol (sun) and sistere (to stand still).
Nowadays, the summer solstice comes and goes with little significance to many.
But for millennia, people around the world celebrated the summer solstice in various ways. Some still take part in festivities.
The most well-known celebration takes place at 5,000-year-old Stonehenge in England.
Crowds of about 10,000 people — including druids and pagans — often gather at Stonehenge to watch as the rising sun aligns perfectly with the complex’s Heel Stone, which stands outside the main circle.
In Scandinavian countries, Midsummer festivals mark the summer solstice. In Sweden, people dance around a maypole and feast on herring and vodka.
Some Alaskans celebrate with midnight baseball, and in Iceland, some celebrate with late-night hiking and golf.
Meanwhile in Ukraine, celebrations honor John the Baptist, known as Ivan Kupala.
This year, astronomical summer concludes with the autumn equinox on September 23.