Everything to Know About the Summer Solstice, the Longest Day of the Year

It's time for long days of rays!

The summer solstice — also known as the "June solstice" — is an astronomical event that signifies the official start of the summer season, while simultaneously marking the longest day of the year.

In contrast to winter's long and dark nights, the summer season brings the most daylight and sunshine because the path of the sun in the sky is the farthest north in the Northern Hemisphere. This takes place throughout June, July, August and mid-September.

Meanwhile, the Southern Hemisphere is entering the winter solstice and experiencing the exact opposite because the sun is the farthest south. Therefore, summer for those below the equator takes place throughout December, January and February.

While the solstices signify the start of winter and summer, planetary scientists also use equinoxes to define the beginning of the autumn and spring seasons.

The word equinox derives from Latin words "aequi" (meaning equal) and "nox" (meaning night). Taking place annually in March and September, equinoxes mark the time when the day and night are approximately equal in length.

Although the solstices and equinoxes traditionally define the start of the astronomical seasons (based on the Earth's position in relation to the Sun), meteorological seasons define the temperature and climatological patterns on Earth (generally, colder in the winter and warmer in the summer).

Keep scrolling for everything to know about the summer solstice, including when and why it takes place.

When is the summer solstice in 2023?

Taking place exactly six months after the winter solstice occurred in December, the summer solstice happens at 10:58 a.m. ET on Wednesday, June 21, 2023.

Why does the summer solstice happen?

The summer solstice happens biannually due to the sun's positioning in relation to the Earth. In the Northern Hemisphere, it falls in June. In the Southern Hemisphere, it takes place in December.

In scientific terms, both solstices are a result of the Earth's tilted axis. The summer solstice occurs when the Earth reaches the point in its orbit when the North Pole is at its maximum tilt of about 23.5 degrees toward the Sun.

Therefore, people north of the equator will experience the longest day and shortest night of the calendar year since the Northern Hemisphere will receive the most direct sunshine of the year. (Note: "longest day" simply refers to the period of maximum sunlight in effect.)

The Earth's tilted axis also explains why the sun doesn’t rise and set at the same locations on the horizon each morning and night. According to the Old Farmer's Almanac, "its rise and set positions move northward or southward in the sky as Earth travels around the sun through the year."

Furthermore, the sun’s path in the sky becomes higher or lower over the course of the year. The summer solstice is significant because the sun is at its northernmost point in the sky, at which point the Sun’s path does not change for a brief period of time.

The word “solstice” comes from the Latin "solstitium." This breaks down into "sol" (sun) and "stitium" (still or stopped).

Does the June solstice mark the official start of summer?

While the summer and winter solstices have become synonymous with representing the official starts of their respective seasons, their starts technically depend on which definition is being used. Seasons can be defined in two ways: astronomically or meteorologically.

Astronomical seasons are based on Earth's position as it rotates around the sun, while meteorological seasons are based on annual temperature cycles. Therefore, the four seasons have different start and end dates depending on the calendar method utilized.

Although exact start times vary between the two methods, they generally fall within the same time periods. The astronomical method pinpoints a specific date across four months to signify the start of each season, while the meteorological method breaks the seasons down into groupings of three months.

Astronomically, winter in the Northern Hemisphere stars in December, spring starts in March, summer starts in June and autumn starts in September. Meteorologically, winter in the Northern Hemisphere includes December, January, and February; spring includes March, April, and May; summer includes June, July, and August; and fall includes September, October, and November.

The Old Farmer's Almanac, regarded as the "calendar of the heavens," uses the astronomical definition to define each of the four seasons.

When is the winter solstice?

This year's winter solstice takes place at 10:27 p.m. ET on Thursday, Dec. 21, 2023.