(Twenty-Four Solar Terms in China)

The 24 solar terms in China are divided based on the position of the sun in the ecliptic and reflect the climatic changes and agricultural activities throughout the year. Here are brief introductions to the 24 solar terms:

SPRING

• Start of Spring (February 3rd–5th): The sun reaches the ecliptic longitude of 315°. “Start” means the beginning. It marks the beginning of spring, with the weather gradually warming up and all things reviving.
• Rain Water (February 18th–20th): The sun reaches the ecliptic longitude of 330°. As the temperature rises, ice and snow melt, and precipitation increases, mostly in the form of light rain.
• Awakening of Insects (March 5th–7th): The sun reaches the ecliptic longitude of 345°. With the first spring thunder, hibernating animals in the soil are awakened. The weather gets warmer, and the busy season for spring farming begins.
• Spring Equinox (March 20th–22nd): The sun reaches the ecliptic longitude of 0°. On this day, day and night are almost equal in length. After that, the sun’s direct rays gradually move northward, with days getting longer and nights shorter in the Northern Hemisphere.
• Pure Brightness (April 4th–6th): The sun reaches the ecliptic longitude of 15°. The weather is clear and bright, and vegetation is lush. It is a good time for spring outings and also a day for ancestor worship and tomb sweeping.
• Grain Rain (April 19th–21st): The sun reaches the ecliptic longitude of 30°. It means “rain nourishes all grains.” Precipitation increases significantly, which is beneficial for the growth of cereal crops.

SUMMER

• Start of Summer (May 5th–7th): The sun reaches the ecliptic longitude of 45°. It marks the beginning of summer. The temperature rises, and the hot summer is approaching. Crops enter the vigorous growth season.
• Grain Buds (May 20th–22nd): The sun reaches the ecliptic longitude of 60°. At this time, the grains of summer crops begin to fill and become plump, but they are not yet mature. It is only “grain buds” and not “grain full.”
• Grain in Ear (June 5th–7th): The sun reaches the ecliptic longitude of 75°. The literal meaning is “grain with awns is ready for harvest, and it’s time to plant grain.” It is the season for sowing late rice and other cereal crops, and also the busy season for summer harvesting, planting, and management.
• Summer Solstice (June 21st–22nd): The sun reaches the ecliptic longitude of 90°. On the day of the summer solstice, the Northern Hemisphere has the longest day and the shortest night. After that, the days gradually shorten and the nights gradually lengthen.
• Minor Heat (July 7th–8th): The sun reaches the ecliptic longitude of 105°. It indicates that the weather begins to get hot, but it has not yet reached the hottest point. People need to pay attention to heatstroke prevention and cooling.
• Major Heat (July 22nd–24th): The sun reaches the ecliptic longitude of 120°. It is the hottest period of the year. The temperature is the highest, and the weather is scorching. People need to pay attention to heatstroke prevention and cooling, and crops are growing vigorously.

AUTUMN

• Start of Autumn (August 7th–9th): The sun reaches the ecliptic longitude of 135°. It marks the beginning of autumn. The weather gradually cools down, but the hot summer is still lingering, with the phenomenon of “autumn tiger.”
• End of Heat (August 22nd–24th): The sun reaches the ecliptic longitude of 150°. It indicates the end of the hot summer. The temperature gradually decreases, and the weather becomes cool and refreshing.
• White Dew (September 7th–9th): The sun reaches the ecliptic longitude of 165°. At this time, the temperature drops, and water vapor in the air condenses into dew at night, which is white and indicates that the weather is getting colder.
• Autumn Equinox (September 22nd–24th): The sun reaches the ecliptic longitude of 180°. On the day of the autumn equinox, day and night are almost equal in length. After that, the sun’s direct rays gradually move southward, with days getting shorter and nights longer in the Northern Hemisphere.
• Cold Dew (October 8th–9th): The sun reaches the ecliptic longitude of 195°. It indicates that the temperature continues to drop. The dew increases and carries a chill, and the weather gets colder.
• Frost’s Descent (October 23rd–24th): The sun reaches the ecliptic longitude of 210°. It means that the weather is getting colder and frost begins to appear, marking the transition from autumn to winter.

WINTER

• Start of Winter (November 7th–8th): The sun reaches the ecliptic longitude of 225°. It marks the beginning of winter. The weather gradually gets colder, and crops are harvested and stored.
• Minor Snow (November 22nd–23rd): The sun reaches the ecliptic longitude of 240°. At this time, the temperature drops, and the northern regions begin to see snowfall, but the amount of snow is generally not large.
• Major Snow (December 6th–8th): The sun reaches the ecliptic longitude of 255°. It means that the amount of snowfall increases and the weather gets colder. The northern regions enter the severe winter.
• Winter Solstice (December 21st–23rd): The sun reaches the ecliptic longitude of 270°. On the day of the winter solstice, the Northern Hemisphere has the shortest day and the longest night. After that, the days gradually get longer and the nights gradually shorter.
• Minor Cold (January 5th–7th): The sun reaches the ecliptic longitude of 285°. It indicates that the weather is cold, but it has not yet reached the coldest point. People need to pay attention to keeping warm.
• Major Cold (January 20th–21st): The sun reaches the ecliptic longitude of 300°. It is the coldest period of the year. The weather is very cold. People need to pay attention to cold protection and crops also need to be protected from freezing.

The 24 solar terms are the products of ancient Chinese agricultural civilization and are of great significance for guiding agricultural production and arranging daily life.