The Summer Solstice: When is the Longest Day of the Year?
Did you know that no consecutive two days of the year have the exact same day length? Yes, the length of the days (the period with daylight, except the night) keep changing from the start of the year to the end of the year on a repeating cycle. In this post, we will talk in detail about the longest day of the year.
In another post, we talked about the Winter Solstice and gave an answer to the question "when is the longest night of the year?" for both hemispheres of the Earth. Now, we will do the same for the Summer Solstice.
The axial tilt of the Earth, which is about 23.5 degrees on average, changes its direction due to the location of the Earth around the Sun, while it is making a full cycle on its orbit throughout the year. When the axial tilt faces towards the Sun, the Northern Hemisphere receives the majority of the sunlight; whereas, when the axial tilt faces away from the Sun, the Southern Hemisphere receives the majority of the sunlight.
The fact that Earth's axis is tilted and that its direction changes slowly every single day during the course of the year causes the natural phenomenon that we name as seasons. A perfect cycle of Summer, Winter, Spring and Autumn seasons depends its existence to the axial tilt of the Earth and how the position of Earth changes relative to the Sun, during their galactic travel together. If the axis was straight, there would be no change of seasons and every point on the Earth would continue to live a static season based on its distance from the Equator.
(Photo by Unsplash)
The magical balance in this equation causes the Northern Hemisphere to experience the Summer, when the Southern Hemisphere is experiencing the Winter and vice versa. While the days are getting longer and longer in the NH, at the same time they are getting shorter and shorter in the SH. During the longest day of the year, the North or South pole are fully illuminated by sunlight, hence they have a day with 24 hours of daylight. There are even some cities in the world such as Reykjavik in Iceland or Fairbanks in Alaska which have days with 21-22 hours of daylights.
Now, let's continue with when the longest days in the Northern and Southern Hemispheres occur.
When is the Longest Day of the Year in Northern Hemisphere?
As the below image demonstrates, the longest day in Northern Hemisphere occurs when the angle between the Earth's axis and the vertical plane of day-night border is at its maximum (about 23.5 degrees), facing towards the Sun.
This is the start of the Summer for the NH and the start of the Winter for the SH. The longest day of the year in the Northern Hemisphere occurs on June 21, every year. While the NH is living the longest day, the SH is living the shortest day.
Northern Hemisphere Longest Day
June 20 - 21
When is the Longest Day of the Year in Southern Hemisphere?
When the Earth axis makes an angle of about 23.5 degrees with the day-night border line and comes to its maximum point, while it is facing away from the Sun, the Southern Hemisphere is going through the longest day of the year. The following image shows how this works:
As you can see from the above image, the SH is receiving more sunlight than the NH and it is entering Summer, while the other side of the world is entering Winter.
The time of the longest day for the Southern Hemisphere is the day of December 21. It may also be observed on December 22 due to some oscillations in the measurements and how Earth moves around the Sun.
Southern Hemisphere Longest Day
December 21 - 22
What to Do In the Longest Days of the Year?
The longest day of the year will have a different length on any location in the world. Depending on how much of daylight you've got, you can plan a nice one-day trip to a beautiful location, visit the parts of your city that you have never visited before or spend some good time with your friends, celebrating the longest day.
As it is also the start of the Summer, enjoy your day as much as you can, but also don't forget that the days will be getting shorter after their peak in the longest day, resulting in the Sun setting slightly earlier every day.
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