Summer Solstice 2025: The First Day of Summer and the Longest Day
The summer solstice is celebrated in some way in almost every culture on the Earth. But what really happens to our planet on this day, and why is it so important to us? Let's find out.
Contents
- Summary
- What is the summer solstice?
- When does summer start in 2025?
- How to celebrate the summer solstice
- Bottom line
Summary
What is it? The summer solstice in one of the Earth’s hemispheres occurs when this hemisphere is tilted the closest to the Sun and receives the maximum daylight.
When is it? In the Northern Hemisphere, the next summer solstice will take place on June 21, 2025. In the Southern Hemisphere, it will occur on December 21, 2024.
Why is it important? The summer solstice marks the first day of summer in astronomical terms. On this day, we experience the longest day and shortest night. Dozens of celebrations around the world are attached to this event.
What is the summer solstice?
Imagine the Earth orbiting the Sun in space. As we know, our planet both revolves around the Sun and rotates around its own axis — an imaginary straight line through the Earth that runs from the North Pole to the South Pole.
This axis is not perpendicular to the Earth’s orbital plane but is tilted at about 23.5°. This is why throughout the year, the North and South poles lean towards the Sun at different angles (if you're having trouble visualizing this motion, watch this video).
So the moment when one of the Earth’s hemispheres reaches its maximum tilt toward the Sun is called the summer solstice in that hemisphere. On this day, it receives the most amount of sunlight, which results in the longest day of the year there.
More: The Earth has four seasons, but it’s not as simple as you think.
When does summer start in 2025?
Summer begins on the day of the summer solstice. For the Northern Hemisphere, it will happen on June 21, 2025.
In the Southern Hemisphere, seasons are reversed. There the summer will start on December 21, 2024. (By the way, this is why astronomers prefer to say June or December solstice and avoid confusion).
But what happens on June 1st? Isn't that the first day of summer? Well, that depends on how you look at it.
Astronomically speaking, a new season on any planet (not just the Earth) begins on either a solstice or an equinox. These natural phenomena were used by our ancestors to mark time for thousands of years; they became the basis for the astronomical calendar. But the dates of the solstices and equinoxes change every year, so the length of the seasons varies between 89 and 93 days, making it difficult to compare seasonal data.
To overcome this, meteorologists and climatologists created meteorological seasons, which divide the year into three-month periods based on annual temperature patterns. These seasons better match our civil calendar and are more consistent, making it much easier to calculate seasonal statistics from monthly statistics. Conveniently, both of them are very useful for various purposes, such as agriculture and commerce.
Summer solstice dates
Note that the dates here are provided for Greenwich Mean Time (GMT). In your local time zone, the dates can vary.
In the Northern Hemisphere, the summer solstice usually occurs on June 20 or 21. Rarely it can occur on June 22, but that won't happen in the 21st century. The next summer solstice on this date will occur in 2203.
In the Southern Hemisphere, the summer solstice most of the time happens on December 21 or 22; it can also rarely fall on December 20 or 23. In this century, only five solstices occur on December 20. The next solstice on December 23 will occur in 2303.
Northern Hemisphere
- 2025: June 21, 02:42 GMT (June 20, 10:42 p.m. EDT)
- 2026: June 21, 08:25 GMT (4:25 a.m. EDT)
- 2027: June 21, 14:11 GMT (10:11 a.m. EDT)
- 2028: June 20, 20:02 GMT (4:02 p.m. EDT)
- 2029: June 21, 01:48 GMT (8:48 p.m. EDT)
Southern Hemisphere
- 2025: December 21, 15:03 GMT (10:03 a.m. EST)
- 2026: December 21, 20:50 GMT (03:50 p.m. EST)
- 2027: December 22, 02:42 GMT (09:42 p.m. EST)
- 2028: December 21, 08:20 GMT (03:20 a.m. EST)
- 2029: December 21, 14:14 GMT (09:14 a.m. EDT)
When do the days start getting shorter?
Days get shorter after the day of the summer solstice. This is the day when people experience the most daylight. Then the days become shorter and shorter, and by the autumnal equinox, the length of day and night are almost equal.
Locations closer to the poles experience greater differences in day length throughout the year, so summer days are longer there. In Whitehorse, Canada, which is far north, the longest day in 2025 will be 19 hours and 09 minutes. In Bogota, Colombia, near the equator, the longest day will last for 12 hours and 23 minutes.
Places within the polar circles experience Midnight Sun or polar day for a few days or months when the Sun does not set at all.
Summer on other planets
Every planet in the Solar System experiences seasons because they all have an axial tilt. Only Mercury has such a small axial tilt that we can't even tell when one season ends and the next one begins. Let's take a look at how long summer lasts on other planets.
- Venus: 55-58 days
- Earth: 89-93 days
- Mars: 7 months
- Jupiter: 3 years
- Saturn: about 7 years
- Uranus: 21 years
- Neptune: more than 40 years
Of all the planets, Uranus has the most interesting seasons due to its extreme axial tilt of 98° (the planet basically rotates on its side relative to the plane of the Solar System). Imagine a summer day that lasts for a quarter of your life! This is the case with Uranus, whose summer half faces the Sun continuously for 21 years. Meanwhile, the other (winter) half of this bizarre planet experiences 21 years of night. But in spring and autumn the situation changes. Around the equinoxes, sunlight hits the equatorial region of the planet. Uranus rotates on its axis every 17 hours and 14 minutes. This means that much of the planet has a fairly normal (for us on the Earth) day-night cycle of 17 hours.
How to celebrate the summer solstice
There are many ways to celebrate the first day of summer around the world — people gather near Stonehenge, dance around a maypole, decorate houses with greenery, burn giant bonfires, and more. As fans of astronomy, we encourage you to get outside and check out the night sky!
You can also start celebrating right now by taking the solstices and equinoxes quiz. Don't wait any longer to see if you're a true astronomy expert!
Bottom line
In 2025, the summer solstice will occur on June 21, at 02:42 GMT in the Northern Hemisphere, and on December 21, 2024 at 09:20 GMT in the Southern Hemisphere. This event marks the beginning of summer in astronomical terms and the longest day. Don't miss it, the days will start getting shorter after that! Celebrate it by going outside and observing the fascinating night sky!
