Welcome, summer! This June 21 marks the summer solstice in the northern hemisphere and, with it, the arrival of the hottest season of the year. This is what you should know about the expected astronomical event.
The science of the summer solstice
The Earth orbits the Sun at an angle. “Its tilted axis always points in the same direction. So, during the year, different parts of the Earth receive the direct rays of the Sun,” explains NASA.
When the Sun reaches its peak in the northern hemisphere, that is the summer solstice.
At that time, “the Sun is directly over the Tropic of Cancer, which is at 23.5° north latitude, passing through Mexico, the Bahamas, Egypt, Saudi Arabia, India, and southern China,” according to the Service. National Weather.
In all places north of the Tropic of Cancer, the summer solstice day is the longest of the year. The days have been lengthening before your arrival and will begin to shorten afterward.
In the Arctic Circle, there are sunlight 24 hours a day, according to the time and data portal. Just because it’s the longest day doesn’t mean it’s the closest sunrise, the site explains. This happens a few days before the solstice, while the latest sunset happens a few days after.
It’s all about lean, not close
The Earth makes a complete return to the Sun every year in an elliptical orbit, so the distance to the star varies depending on the moment.
The moment when it is closest to the Sun is called perihelion and it happens in January. The one farthest from the star, meanwhile, is known as aphelion and happens in July. Therefore, it does not coincide with the solstice: the solstice is linked to the tilt of the Earth and not to its proximity.
It is the inclination and not the proximity, consequently and contrary to what you might think, that determines the seasons, according to the explanation of the National Weather Service.
At what exact time will the summer solstice be?
Tuesday, June 21, but at what exact time? The solstice occurs at 09:13 UTC. The specific answer to the question, therefore, will depend on where you are in the world. Here we give you the reference of the local time of the solstice in some of the big cities of the United States and Europe:
- Miami: 05:13
- Mexico City: 4:13
- Los Angeles: 2:13
- London: 10:13
- Madrid: 11:13
The site explains that, although many people consider that the solstice always occurs on June 21, it can occur between the 20th and the 22nd. The cases of the solstice on the 22nd are rare, according to the review: the last one was in 1975 and the next one will be in 2203.
What happens in the south meanwhile?
The southern hemisphere, meanwhile, is preparing for the opposite situation: June 21 sees the shortest day of the year and with it the arrival of winter. From the 21st onwards, however, the days begin to lengthen until the December solstice, when summer enters.
In the last month of the year, while the south celebrates the summer solstice, the north celebrates the winter solstice, which marks the shortest day and the longest night. This occurs when “the Sun is directly over the Tropic of Capricorn, located 23.5 ° south of the equator and which crosses Australia, Chile, southern Brazil, and northern South Africa,” according to the explanation of the Meteorological Service National.