As we move through the annual cycle of solar terms, each phase brings its unique charm and significance. Among them, “Slight Heat” holds a special place. Falling between July 22nd and 24th on the Gregorian calendar, Slight Heat, or “Xiaoshu” in Chinese, represents a subtle transition from the mild warmth of early summer to the upcoming hot days of midsummer. This solar term not only marks changes in weather patterns but also carries cultural and agricultural implications. Let us delve into the essence of Slight Heat and explore the beauty it encapsulates.
what does slight heat China?
“Xiaoshu” is the 11th solar term in the traditional Chinese calendar, marking the end of the month of Wu and the beginning of the month of Wei. It falls between July 6th and 8th in the Gregorian calendar when the sun reaches the celestial longitude of 105 degrees. “Shu” means heat, and “Xiaoshu” represents a relatively mild heat compared to the upcoming solar term, “Dashu,” which is the hottest period of the year. There is a saying in folk culture: “Xiaoshu Dashu, up steaming and down boiling.” During Xiaoshu, many regions in China experience frequent thunderstorms.
Xiaoshu marks the beginning of the hottest period of the year known as the “three fu days.” The three fu days are typically between Xiaoshu and Chushu, characterized by the highest temperatures, humidity, and sultriness of the year. The monsoon climate is a prominent feature of China’s weather, with the summer season influenced by warm and humid airflows from the ocean. Although Xiaoshu brings intense sunlight, high temperatures, humidity, and rainfall, it is beneficial for the growth of crops.
In the past, there were traditional customs associated with Xiaoshu in different regions of China. In the southern regions, people would celebrate “Shi Xin” by tasting newly harvested rice after Xiaoshu. Farmers would mill the newly harvested rice and cook it as an offering to the gods and ancestors. In the northern regions, people have the tradition of eating dumplings during the first fu day. During the fu days, people often have a poor appetite and may experience weight loss. Dumplings are considered appetizing and satisfying, and their shape resembles gold ingots, symbolizing wealth. Eating dumplings represents the wish for abundant fortune.
slight heat history of China
The twenty-four solar terms in the Chinese calendar represent the natural rhythm of seasonal changes and establish specific points in time, known as “twelve-month junctures,” that accurately reflect these changes. These terms carry profound cultural significance and historical accumulation. Wu Cheng, a scholar from the Yuan Dynasty, wrote in his book “Gathering Explanations of the Seventy-Two Hou of Monthly Ordinances”: “The June term… Slight Heat, meaning heat, is further divided into small and large. The beginning of the month is small, and the middle of the month is large. Nowadays, the heat is still relatively mild.”
Slight Heat, as the name suggests, refers to a period of slight heat during which the weather becomes warm, but it is not yet the hottest time of the year. The folk saying goes, “Slight Heat is not very hot, but the three Fu days of Major Heat are.” This indicates that the hottest period of the year has arrived, but it has not yet reached its peak intensity.
During Slight Heat, we experience the beginning of scorching summer days. It signifies the onset of the hottest season, although it is not the peak of summer heat. The saying goes, “The heat resides within the three Fu days.” The three Fu days fall between Slight Heat and End of Heat, and they are the hottest and most humid period of the year. The monsoon climate is a dominant feature of the Chinese climate, characterized by a combination of continental and maritime influences. In summer, it is influenced by warm and moist air currents from the ocean, resulting in high temperatures, humidity, and abundant rainfall. The period of high temperature and heavy rainfall aligns well with the growth of crops. Slight Heat, with its hot weather and frequent thunderstorms, marks a time of vigorous growth for all living things.
Changes in weather during the slight heat
The slight heat marks the eleventh solar term in the Chinese calendar, representing the transition from the solar term of “wu” to “wei.” In the Northern Hemisphere, the daylight hours gradually shorten during this period. However, the temperatures in most parts of China continue to rise. This is because although the sun’s zenith point shifts southward, it still shines directly on the Northern Hemisphere. The heat received by the Northern Hemisphere exceeds the heat dissipated, leading to a continuous increase in temperatures. In southern regions, the average temperature during the slight heat is around 26 degrees Celsius. By mid-July, in low-altitude river valleys of South China and Southeast China, the average daily temperature can exceed 30 degrees Celsius, with the daily maximum temperature surpassing 35 degrees Celsius. In contrast, the northern part of the Northwest Plateau can still experience frost and snow, resembling the scene of early spring in South China.
During the slight heat, we enter the period of Fu Tian, which is characterized by increased humidity. The high humidity during the three Fu days is due to the southeast winds blowing from the Pacific Ocean and the Indian Ocean. The moist air from the sea contributes to the high humidity during this period. “Fu Tian” is a climate characteristic of southern China, marked by high temperatures and high humidity, while the northern regions experience high temperatures with dry conditions. Slight heat refers to a period of mild heat, which is not yet the hottest time of the year. After the slight heat, cool breezes become rare, and the wind carries heatwaves. The monsoon climate is the dominant feature of the Chinese climate, influenced by warm and moist air currents from the ocean during the summer. Many parts of China experience high temperatures, humidity, and abundant rainfall during this time. Thunderstorms are common during this season, accompanied by strong winds and heavy rain. The frequency of tropical cyclones increases, with more tropical cyclones making landfall in China. In summary, the climate characteristics of the slight heat period are hot weather and an increase in thunderstorms.
After the slight heat, South China, Southwest China, and the Qinghai-Tibet Plateau enter the southwest monsoon rainy season influenced by the Indian Ocean and the South China Sea. The middle and lower reaches of the Yangtze River are generally under the control of the subtropical high-pressure system, experiencing hot and dry weather with little rainfall. In some years, the influence of cold air from the north remains strong before and after the slight heat, resulting in frontal thunderstorms in the middle and lower reaches of the Yangtze River as warm and cold air masses clash. The thunderstorms during the slight heat period often indicate the arrival of the rainy season, which may persist for some time in the middle and lower reaches of the Yangtze River.
In northern regions of China, the rainy season has not yet arrived during the slight heat period. China has a typical monsoon climate, and the distribution of rainfall is mainly controlled by large-scale atmospheric circulation systems such as the subtropical high-pressure system over the northwest Pacific Ocean. From mid-June to early to mid-July, the main rainfall belt in eastern China generally extends northward from South China and the Jiangnan region to the middle and lower reaches of the Yangtze River or the Jianghuai region. By late July, with the northward movement of the subtropical high-pressure system, the southwest monsoon also advances northward. The southwest winds on the periphery of the subtropical high transport warm and moist air masses from tropical and subtropical regions to northern regions. The interaction between the warm and moist air and the cold air from the mid-latitudes occurs in North China and Northeast China, marking the beginning of the rainy season in these regions. The period from late July to early August, known as “Qi Xia Ba Shang,” signifies the rainy season in northern regions of China, including North China and Northeast China.
Phenomena during the slight heat
In the book “Collection and Explanation of the 72 Phenomena of the Monthly Ordinances” by the Yuan Dynasty scholar Wu Cheng, based on the characteristics of the 24 solar terms combined with the surrounding landscapes of the Yellow River Basin, the 24 solar terms are further divided into “72 Phenomena,” with each solar term consisting of three phenomena. The three phenomena during the slight heat are as follows: “The first phenomenon is the arrival of warm winds; the second phenomenon is the presence of crickets in houses; the third phenomenon is the beginning of the shrill cry of eagles.” During the slight heat, there is no longer a trace of cool breeze on the land, but all winds carry heatwaves. The Book of Songs, in the poem “Seventh Month,” describes crickets: “In the seventh month, they are in the fields; in the eighth month, they are in the houses; in the ninth month, they are at the door; in the tenth month, crickets enter under my bed.” The mentioned eighth month corresponds to the sixth month in the lunar calendar, which is the time of the slight heat solar term. Due to the heat, crickets leave the fields and seek refuge from the summer heat in the corners of courtyards. During this solar term, eagles soar in the cool high skies due to the excessively high ground temperatures.
Agricultural Activities during Slight Heat
During the period of slight heat, the southwestern regions of China enter the season with the most frequent heavy rains. The months of July and August often account for more than 75% of the annual rainy days, lasting for approximately three days. However, in the eastern parts of South China, after the slight heat, the region is often influenced by the subtropical high pressure, resulting in dry and hot weather, marking the beginning of a potential drought. The climate pattern of alternating drought in the east and floods in the west in most parts of southern China is closely related to agricultural productivity. It is crucial to implement early drought resistance and flood prevention measures to mitigate potential damages. The southwestern regions, including South China, Southwest China, and the Qinghai-Tibet Plateau, experience the monsoon season influenced by the Indian Ocean and the South China Sea. Meanwhile, the middle and lower reaches of the Yangtze River are generally under the control of the subtropical high pressure, resulting in high temperatures and less rainfall. The onset of drought during this period significantly affects agricultural production, emphasizing the importance of early water storage and drought prevention.
Before and after the slight heat, apart from harvesting winter and spring crops such as wheat, the focus of agricultural activities shifts to field management. Early rice enters the grain filling stage, and early-maturing varieties are harvested before the arrival of the major heat period. Proper water management is essential during this time. Middle-season rice enters the booting stage, requiring additional fertilization based on its growth condition to promote spike development and increase grain yield. Late-season rice is in the tillering stage, and timely application of tiller fertilizers is necessary. Precautions should be taken to prevent diseases and pests in the seedlings, with sufficient fertilizer applied 5 to 7 days before transplanting. The hot summer weather during this time is conducive to the proliferation of aphids, red spider mites, and other pests. Timely prevention and control of diseases and pests are crucial for effective field management.
During the slight heat period, early rice and spring corn are in the grain filling and milky ripening stages, which are critical for grain formation. Agricultural activities focus on preventing premature aging, promoting grain filling, and increasing grain weight. It is important to take precautions against premature ripening and drought. Measures such as irrigation can be implemented to improve the microclimate in the fields during extreme heat (above 35°C) or dry conditions. Middle-season rice and summer corn are in the transition period from vegetative growth to reproductive growth, requiring substantial water supply. Premature water shortage for middle-season rice hampers effective tiller formation and young panicle differentiation, leading to potential yield reduction. Summer corn may suffer from necking due to drought, resulting in severe yield loss. Cotton is at the flowering stage, while late-season rice is in the seedling stage, requiring attention to maintaining open channels to prevent waterlogging. Furthermore, the favorable weather conditions during slight heat provide an opportune time for disease and pest control operations in the fields.
Before and after slight heat, most parts of southern China experience a period with the highest frequency of thunderstorms. Thunderstorms are intense weather phenomena often accompanied by strong winds, heavy rainfall, and occasionally hail, which can lead to disasters. In the eastern parts of South China, after the slight heat, the region is often influenced by the subtropical high pressure, resulting in dry and hot weather, entering the potential drought period. The climate pattern of alternating drought in the east and floods in the west is a characteristic of most parts of southern China.
Traditional Customs during Slight Heat
There are several traditional customs observed during the slight heat period in China, including “eating new food,” “eating dumplings,” and “eating stir-fried noodles.” Additionally, on the sixth day of the sixth month in the lunar calendar, there is a custom of sun-drying books, paintings, and clothing. It is believed that sun-drying them on this day can prevent damage from insects, hence the saying “On the sixth day of the sixth month, sun-dry in red and green.”
Custom of “Eating New Food”
In the past, there was a folk custom in southern China of “eating new food” during slight heat. “Eating new food” involved grinding newly harvested rice, wheat, and other grains into flour and making various types of pancakes and noodles to be shared among neighbors and friends. It was a way to express wishes for a bountiful harvest. Additionally, a portion of the new produce would be prepared for ancestral worship, seeking blessings for favorable weather conditions.
In northern China, there is a saying that goes, “Dumplings in the first heat, noodles in the second heat, and pancakes with eggs in the third heat.” Eating dumplings during the first heat is a traditional custom. During the hot days, people often have a reduced appetite and may appear thinner than usual, known as the “hard summer.” Dumplings are considered appetizing and satisfying in traditional customs. Dumplings have long been a beloved food in the vast northern regions of China, and there is a saying, “Nothing tastes better than dumplings.”
Slight Heat represents more than just a transition from one season to another. It symbolizes the interconnectedness of nature, culture, and human life. As we honor this solar term, let us cherish the beauty it brings and embrace the spirit of change and growth. May we find harmony in the warmth of Slight Heat, appreciating the delicate balance between nature’s rhythms and our own existence in this ever-changing world.