What Time Is Summer Solstice and When Is the Longest Day of 2022?

The June solstice is almost upon us, marking the longest day of the year in the Northern Hemisphere.

This solstice also marks the beginning of summer—according to the astronomical definition—in the northern half of the globe. The opposite is true in the Southern Hemisphere, where the June solstice marks the shortest day of the year and the beginning of astronomical winter.

While the term "summer solstice" is often used to refer to the longest day of the year in its entirety, technically, this astronomical phenomenon occurs at a specific moment in time—when our planet reaches the point in its orbit where the North Pole is at its maximum tilt toward the sun. At this time, the sun is directly above the Tropic of Cancer.

In 2022, the Northern Hemisphere summer solstice will occur at 5:14 a.m. ET on Tuesday, June 21, according to The Old Farmer's Almanac.

On the June solstice, the sun will reach its highest point in the Northern Hemisphere sky—for regions outside of the tropics—and will take the longest route between rising and setting.

As a result, June 21 will have the most hours of sunlight and the shortest night of 2022 in the Northern Hemisphere. This effect becomes less and less noticeable as you move closer to the equator.

Sunset over Manhattan
New York, will experience more than 15 hours and five minutes of daylight on June 21. a stock image of sunset over Manhattan with sunbeams between buildings. iStock / Getty Images

Long Day in New York

For example, New York, will experience more than 15 hours and five minutes of daylight on June 21. Tropical regions of the Northern Hemisphere, meanwhile, will see just over 12 hours of daylight, whereas in the Arctic Circle, the sun will not set.

The reason we have solstices is that the Earth is tilted on its axis by around 23.4 degrees relative to the plane of its orbit. As a result, both hemispheres spend six months of the year tilted towards the sun, and the other half tilted away.

According to Robert Massey, deputy executive director of the U.K. Royal Astronomical Society, our planet's tilt means that it's pointing to roughly the same place in the sky throughout the year—in the direction of the pole star.

"In the summer months in the Northern Hemisphere, the northern part of the Earth is tilted towards the sun. And in the winter months, the Northern Hemisphere is tilted away from the sun," Massey told Newsweek.

"So if you imagine this planet going around the sun in a rough circle and that axis is pointing to the same bit in the sky, then there will be times when we are leaning towards the sun and other times when we're leaning away."

This is what produces the seasons on Earth. When the Northern Hemisphere is tilted toward the sun, for example, it receives radiation at a more direct angle, leading to warmer temperatures—what we call summer. In winter, the opposite is true.

Again, as you move closer to the equator, this effect becomes less noticeable. In tropical regions, radiation from the sun is more constant over the course of the year, which is why these areas don't experience distinct summers and winter seasons like temperate and polar regions.

The June solstice marks the beginning of the Northern Hemisphere's summer in astronomical terms. But there is also another definition used to denote the start of the seasons—one which is based on annual temperature cycles rather than the orbit of the Earth around the sun. According to this meteorological definition, summer actually started on June 1.

People have been marking the summer solstice since ancient times. Among the most famous examples is Stonehenge in southwestern England, which was built around 4,500 years ago.

The people who built the famous monument clearly considered the solstices to be a significant occasion because it was constructed in such a way that the stones frame the sunrise at the June solstice and sunset at the December solstice. Thousands of people still flock to the prehistoric site today to celebrate the solstices.

The Kukulcán pyramid constructed by the ancient Maya civilization at Chichen Itza in what is now Mexico is also aligned around the rising of the sun at the summer and winter solstices.

The summer solstice at Stonehenge
A file photo of Stonehenge during the summer solstice in 2018. The ancient monument was constructed in such a way that the stones frame the sunrise at midsummer and sunset at midwinter. iStock