The Summer Solstice is one of the 24 solar terms in the agricultural calendar. It is also a very special time of the year that marks the official beginning of summer.
When is the Summer Solstice?
The Summer Solstice is the day when the duration of daylight is the longest in the Northern Hemisphere, while it is the shortest in the Southern Hemisphere. According to Western astronomy, this day marks the beginning of summer in the Northern Hemisphere and the start of winter in the Southern Hemisphere. From the Eastern perspective, the Summer Solstice is considered the mid-summer day, as the character “Chí” (至) in “Hạ Chí” (夏至) means it has reached its peak. On this day, the Sun will be at its highest point in the northern sky at noon before gradually returning south.
Every year, the Summer Solstice typically begins around June 21 or 22 (marking the end of the Grain Rain solar term) and ends around July 6 to 8 (when the Minor Heat solar term begins). Thus, in the year 2024, the Summer Solstice falls on June 21, which is the day when the sun shines the most of the year, nearly a quarter of a minute longer than 24 hours.
On the Summer Solstice, the sunset is the longest of the year. (Photo: Meg-moir)
Why is the Summer Solstice the longest day of the year?
When the Summer Solstice begins, the Earth is tilted at 23.5 degrees on its axis. On June 21 (or sometimes June 20), the North Pole is oriented most towards the Sun. Generally, the Winter Solstice occurs when the upper half of the North Pole faces directly away from the Sun while the South Pole is shrouded in darkness.
The Northern Hemisphere of the Earth tilts most towards the Sun during the Summer Solstice. (Graphic: timeanddate.com. Translation: Ftvh).
Tuesday marks the peak of the sun’s position but is not necessarily the hottest day due to the ocean temperatures gradually decreasing. By mid-June, the oceans in the Northern Hemisphere still retain the “cool” temperatures from the previous winter.
Compared to winter, during summer, the Earth is actually farther from the Sun because the Earth’s orbit is elliptical, leading to a change in the distance from the Earth to the Sun. This distance can differ by about three million miles (five million kilometers), resulting in the Earth’s thermal radiation being 7% greater than on average days.
If you are a science enthusiast, you will find that the Summer Solstice has the longest sunset of the year. At sunset, the temperature at the base of the Sun is approximately between 12-18 degrees Celsius.
The solstices occur twice a year, once in summer known as the Summer Solstice in June, and once in winter known as the Winter Solstice in December. On the Summer Solstice, the Sun is at its highest point in the northern sky, while on the Winter Solstice, it is at its highest point in the southern sky.
The Summer Solstice is unique, corresponding to different hours at each location and thus also corresponding to different days. However, in locations further east, the time zone differences can lead to a deviation in the day.
The Summer Solstice does not occur at the same time in different years. This is because the Earth’s orbit around the Sun is not a perfect circle—specifically, it is about 365.2422 days (which is why leap years with 366 days are necessary to make up for that excess). Additionally, the Earth’s axis itself wobbles over time, making the Summer Solstice (as well as the Winter Solstice, the Spring Equinox, and the Autumn Equinox) not a fixed point in every year but rather variable. Thus, at the same location, the Summer Solstice can fall on June 21 or 22 depending on the year, not always on the same day.
When the Summer Solstice begins, the Northern Hemisphere tilts significantly toward the Sun at 23.5 degrees, resulting in an abundance of light. This leads to the duration of daylight during this solar term being the longest of the year, with days longer than nights, and a gradual process of darkness and light. In fact, the daylight can be so long that some cities in Northern Europe experience a phenomenon known as “white nights”, where night does not occur at all.
The Significance of the Summer Solstice
In terms of agricultural production, construction activities during this period often face challenges due to hot weather, which is frequently accompanied by rain that affects the quality and efficiency of work. If you plan to build or renovate, it is advisable not to choose this season but to undertake work in the dry season for better results.
The Summer Solstice marks the official start of summer according to the Gregorian calendar. It brings the longest day and shortest night of the year for 88% of those living in the Northern Hemisphere. It is also a time for many festivals in the West, such as the Stonehenge Summer Solstice Festival, Denmark’s Sankt Hans Aften, and the Wicca Litha Festival, one of the eight Sabbat celebrations of modern polytheistic practitioners (neopagans)…
This year’s Summer Solstice falls exactly on June 21.
How Does the Summer Solstice Affect Humans?
During this time, the weather is usually extremely hot, humid, and dry, with clear skies. The Trade Winds and Monsoon Winds are strong over the seas, often causing condensation of moisture that leads to heavy rains, floods, and natural disasters that negatively impact people’s lives. Additionally, during the Summer Solstice, the weather is variable, which can lead to individuals contracting illnesses such as colds, heatstroke, flu, dengue fever, malaria, and environmental pollution… Therefore, we need to take proactive measures to prevent illness to maintain our health.
In agricultural production, construction activities during this period often encounter difficulties due to hot weather and frequent rain that affect the quality and efficiency of work.
For farmers during the Summer Solstice, they are often quite busy with fieldwork. Activities like caring for and weeding crops occur during this time to ensure that plants develop robustly and yield the best results.
If you plan to build or renovate, it is advisable not to choose this season but to undertake work in the dry season for better results.
The hot and humid weather during the Summer Solstice and frequent rains encourage vigorous growth of flora and fauna. Plants actively photosynthesize, replenishing and accumulating nutrients in preparation for the upcoming dry season. Meanwhile, animals are also increased in foraging and storing food in preparation for fall and winter. It is also a time when they engage in mating and reproduction, as the nutrient supply for raising offspring is abundant.
Moreover, the hot and humid weather, along with its variable nature, creates favorable conditions for harmful organisms, bacteria, and microorganisms to thrive. Especially, pathogens that cause digestive diseases or mosquitoes that transmit dengue fever… Therefore, people also need to pay special attention to their health, adopting reasonable habits and work practices to avoid illness.
Interesting Facts About the Summer Solstice That Few People Know
The Earth is farthest from the Sun: Many people think that during the Summer Solstice, the Earth is closest to the Sun due to receiving a lot of light and radiation, but in fact, on this day, the distance from the Earth to the Sun is at its farthest point of the year. This is because just weeks after the Summer Solstice, the Earth will move to the point of Aphelion (the farthest point from the Sun) in its orbit.
The Summer Solstice is not exclusive to Earth: Not only Earth but all planets in the solar system have their own Summer Solstice. Accordingly, Mars’ Summer Solstice occurs a few days after Earth’s, and Uranus experiences its Summer Solstice once every 84 years.
The Summer Solstice is not the hottest day of the year: The Summer Solstice receives the most sunlight and solar radiation, but that does not mean it is the hottest day of the year. In reality, the hottest days in the Northern Hemisphere typically fall in July or August when continents and oceans heat up, resulting in higher temperatures, a phenomenon known as “seasonal lag”.
