The longest day of the year is coming. This Sunday is the summer solstice, which also marks the official start of summer.
The summer solstice — also known as the June solstice — occurs when the sun travels along the northernmost path in the sky, according to The Old Farmer’s Almanac.
June 21 isn’t always the date of the summer solstice; depending on the year, it can be on June 20 or 22. During leap years, it often falls on June 20, per BBC. The solstice will occur at exactly 2:24 a.m. MDT early Sunday
What is the summer solstice?
This solstice occurs when “Earth arrives at the point in its orbit where the North Pole is at its maximum tilt (about 23.5 degrees) toward the Sun, resulting in the longest day and shortest night of the calendar year,” per The Old Farmer’s Almanac.
The tilt of the Earth is what makes seasons happen. In June, the Northern Hemisphere is tilted toward the sun, causing longer days and more direct sunlight. In December, it is tilted away from the sun, leading to shorter days and lower sun angles.
On the day of the June solstice, the Northern Hemisphere receives sunlight at the most direct angle it does all year. The longest day of the year means the longest period of sunlight hours. For people who live in the Southern Hemisphere, the June solstice is the shortest day of the year.
According to the National Weather Service, the summer solstice happens when the sun is directly over the Tropic of Capricorn, which runs through Chile, Australia, northern South Africa and southern Brazil.
The word solstice stems from the Latin words sol (sun) and sistere (to stand still), referring to how the sun’s apparent path across the sky appears to pause briefly before turning back southward.
Is the summer solstice the start of summer?
There are multiple ways to define the start of summer, according to Cleveland.com. The summer solstice is the start of astronomical summer, but meteorological summer started on June 1.
Astronomical seasons are determined by the Earth’s position in its orbit around the sun and the tilt of its axis. These seasons start with solstices and equinoxes that happen at roughly the same time every year but not on the same calendar date.
On the other hand, meteorological seasons are split into three-month periods based on the annual temperature cycle.
While the summer solstice marks the start of summer for the Northern Hemisphere, it represents the start of winter for the Southern Hemisphere.