The most abundant day of sunshine in the Northern Hemisphere has arrived as the summer solstice took place on Friday, June 20th. This marks the longest daylight day of the year in the regions north of the equator and signals the official start of summer astronomically. In the Southern Hemisphere, the opposite is happening with the shortest daytime and longest nighttime at the winter solstice.
According to astronomical calculations, the 2025 summer solstice occurred at 10:42 a.m. Beijing time on June 20th, when the sun was directly over the Tropic of Cancer. It is the moment when the sun reaches its highest angle and covers the greatest arc in the northern hemisphere throughout the year.
The term “solstice” comes from the Latin words “sol” (sun) and “stitium” (standstill), symbolizing the sun’s daily trajectory reaching its highest point and seeming to briefly “stand still.” For those who love sunlight, it also signifies that the sun will begin to “retreat,” with daylight hours shortening each day until the winter solstice in late December.
As the Earth revolves around the sun, its axis is tilted about 23.5 degrees, causing uneven distribution of sunlight and heat between the northern and southern hemispheres. The solstices mark the most extreme points of the Earth’s axis tilt toward the sun, resulting in the greatest difference in day and night lengths.
During the northern hemisphere summer solstice, the Earth’s northern tip faces the sun, leading to the longest sunlight exposure and shortest nighttime. The summer solstice usually falls between June 20th and 22nd each year, while the winter solstice occurs between December 20th and 23rd.
The spring equinox and autumn equinox, on the other hand, take place in March and September each year when the Earth’s axis and orbit are aligned, causing almost equal daylight in both hemispheres. The term “equinox” comes from the Latin words “aequus” (equal) and “nox” (night), indicating a close balance in daytime and nighttime lengths.
On the days of the spring and autumn equinoxes, the sun is directly overhead at noon at the equator, making it the only time of the year when both the North and South Poles are illuminated simultaneously by sunlight.
For centuries, humans have marked the arrival of the summer solstice with architecture and festivals. Stonehenge in the UK, designed to align with the sun’s rising and setting paths, still attracts people to gather and watch the sunrise on the morning of the summer solstice.
In Nordic regions like Sweden and Finland, “Midsummer” is a significant cultural celebration representing harvest and love, symbolizing the peak of sunlight and vitality. In the Chinese calendar, “summer solstice” is one of the twenty-four solar terms, traditionally observed with customs such as eating noodles and worshipping ancestors to celebrate abundance and pray for a fruitful year.
In the weeks surrounding the summer solstice, areas north of the Arctic Circle (such as Tromso in Norway, Greenland, and Alaska) experience the phenomenon of “midnight sun,” where the sun remains above the horizon all night. Meanwhile, regions south of the Antarctic Circle enter a period of several weeks known as “polar night,” with darkness persisting throughout the night.
The astronomical four seasons are divided based on the Earth’s orbit and the position of the sun: spring equinox, summer solstice, autumn equinox, and winter solstice mark the turning points. Meteorological seasons, on the other hand, are determined by temperature and climate patterns, dividing the year into four equal periods: spring (March to May), summer (June to August), autumn (September to November), and winter (December to February).
Both classifications serve their purposes: meteorologists and climate researchers prefer meteorological seasons, while solar terms and cultural observations are often based on astronomical seasons.