Is it true that it will rain during Qingming Festival?

Audit expert: Zhan Mingjin

PhD, Chinese Academy of Meteorological Sciences

Are you going out for an outing?

When spring comes, many people like to go out for an outing. For workers, holidays are especially precious. We finally waited for the Qingming holiday, but the bad thing is that the weather is always bad around the Qingming solar term, and it often rains , which prevents us from going out for fun.

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Some people are wondering why it rains every Qingming Festival? Is this an illusion, or is there some truth to it? After some research, the editor finally found the answer.

What is “Qingming Festival”?

The fifth day of the third lunar month every year is the fifth of the 24 traditional Chinese solar terms - Qingming .

In fact, the "Qingming Festival" we talk about in our daily life is actually not just the Qingming solar term.

The day before Qingming Festival, which is the fourth day of March, is called Cold Food Festival, which is the day we mourn our ancestors and worship their ancestors and sweep their tombs. The day before Qingming Festival, which is the third day of March, is called Shangsi Festival, which is mentioned in the Book of Songs: Zheng Feng, "The men and women are holding the jiān (jiān)", and on this day, people go out together to enjoy the spring, and they are so happy.

Source: pixabay

The Qingming Festival is a festival that combines the three days of Qingming, Shangsi Festival and Cold Food Festival. The Qingming Festival is mainly about tomb sweeping and ancestor worship, and it also includes outings and many folk customs. It was officially established during the Song and Yuan dynasties.

So why do we think that Qingming Festival is often associated with rain? Is it true that the great poet Du Mu wrote that "it rains heavily during the Qingming Festival"?

Does it really rain during the Qingming Festival?

If we want to know whether Qingming Festival is really “inseparable from rain”, we can get a glimpse of it from the data.

According to data from China Weather Network, in the nearly 30 years from 1991 to 2020, the top ten cities with a higher probability of rainy days (daily rainfall ≥ 0.1 mm) around the Qingming solar term (April 5 to April 19) are Changsha, Nanchang, Fuzhou, Guiyang, Guangzhou, Hangzhou, Chongqing, Chengdu, Wuhan and Nanning. These cities are all located in the south, and the probability of rainy days exceeds 40%, with the highest reaching 60.7%.

Source: China Weather Network

In terms of rainfall, from 1991 to 2020, among the provincial capital cities with heavy rainfall before and after the Qingming Festival, the area with the highest rainfall was Nanchang, reaching 124.1 mm; Changsha and Guangzhou ranked second and third, with rainfall exceeding 80 mm.

Source: China Weather Network

From this we can see that the heavy rain during Qingming Festival is not our illusion. So, why does it rain during Qingming Festival?

Why does it rain in the south during Qingming Festival?

According to its causes, rainfall is divided into four categories: convective rain, frontal rain, orographic rain and typhoon rain. The rain in the south during the Qingming Festival mainly belongs to frontal rain.

The so-called front is the interface where cold and warm air masses meet. Since warm air is lighter, it is lifted above the cold air and gradually condenses to form rain when the temperature drops.

Schematic diagram of the formation of a front

Source: People's Education Press High School Geography Selective Compulsory Course 1 Textbook

During the Qingming Festival, the cold air from the north weakens, while the warm air from the ocean becomes dominant. The warm air mass slowly rises along the cold air mass, forming a warm front. Since the warm front moves slowly, it generally brings continuous precipitation rather than sudden rainstorms. This is why it rains heavily rather than heavily during the Qingming Festival.

Source: Baidu Encyclopedia

In the eastern region of my country, the frontal rain belt moves seasonally. Wherever the rain belt moves, it will enter a rainy period. On the contrary, areas not covered by the rain belt have less precipitation.

In late spring (around April-May), the rain belt is mainly located in southern China, bringing more precipitation, commonly known as "Dragon Boat Water". At this time, it is still far from the rainy season in the north (around late July-early August). Due to the rapid rise in spring temperature, evaporation intensifies, and the lack of vegetation on the surface, the exposed sand will form sandstorms when encountering strong winds. According to statistics from China Weather Network, from 1991 to 2020, among the 24 solar terms, the average number of days with more sandstorms is concentrated during the Qingming and Guyu periods.

Source: China Weather Network

In addition to frontal rain, convective rain may also occur in southern China. After the spring equinox, the sun's direct point reaches the northern hemisphere and continues to move northward. The solar radiation received by China increases, the ground continues to heat up, the air expands and rises due to the heat, and the water vapor cools and condenses, forming convective rain. This type of precipitation has a small range, short duration, and changes quickly.

If cold air happens to hit, the cold and warm air currents will collide violently, resulting in severe convective weather such as thunderstorms, hail, and short-term heavy rainfall. From March to April, convective rain mainly occurs in southern China, and in May, convective weather begins to enter a high incidence stage across the country.

In addition to rain and windy sand, the phenomenon of "late spring cold" often occurs around Qingming Festival. Why is this?

Why is there a late spring cold snap around the Qingming Festival?

Late spring cold, as the name suggests, is a phenomenon of sudden warm and cold temperatures in spring. The occurrence of late spring cold has nothing to do with Qingming Festival. It just happens to occur between March and May and can occur in both the south and the north.

According to the "Meteorological Indicators for Late Spring Cold" (GB/T 34816-2017) formulated by my country in 2017, late spring cold refers to the phenomenon that the temperature in the early spring is warm and the later spring is cold every year, and the temperature in the later spring is significantly lower than that in normal years.

Source: pixabay

Since every spring is the stage when my country's winter monsoon is about to turn into summer monsoon, the cold air moving south is more active during this period. If the cold air moves south late and with great intensity, the phenomenon of "late spring cold" will occur.

In addition to causing a drop in temperature, late spring cold also has an impact on human health. For people with respiratory diseases, cardiovascular and cerebrovascular diseases, a sudden drop in temperature can easily induce underlying diseases, so special attention should be paid.

In addition, late spring cold weather can cause agricultural products such as early rice seedlings to suffer from low temperature frost damage, and can also cause a significant reduction in the yield of fruit trees such as peaches and grapes. Fortunately, with the development of agricultural science and technology and the maturity of weather forecasting technology, agricultural workers can pay attention to weather conditions at any time and take preventive measures in a timely manner.

Source: Baidu Encyclopedia

"Pear blossoms are in full bloom during the Qingming Festival." Qingming Festival can be said to be one of the most important solar terms in spring. In the upcoming festival, why not share these Qingming tips with your relatives and friends?