Every year after the arrival of the small summer festival will not be long after the "three volt days", the folk also have "small summer is not hot, the summer three volt days" saying, used to describe the sweltering heat of the three volt days, at this time the heat is unbearable, even in the evening the weather is also very hot, making people feel uncomfortable, out of the door will not be long after the hot sweat.
Today, the annual "three volt days" arrive, the ambush time is July 11, of which the initial ambush is 10 days, the middle volt is a total of 20 days from July 21 to August 9, the last volt is 10 days from August 10 to August 19, and this year's three volt days total 40 days. In these days, high temperature, high humidity and high heat will continue to appear, so that everyone can experience the feeling of "steaming sauna".
As early as the Qin and Han Dynasties, there was already a "three volts" saying, usually from mid-July to mid-August, and the high temperature would continue to progress. So is it hot on a three-volt day? From the official meteorological data from 1991 to 2020, in north China, Huanghuai, and the eastern northwest region, the time for the extreme high temperature to break through 40 ° C is 5-7 days; in the south, due to the rain and humidity, the extreme high temperature will not be too high, but the persistence is long, averaging more than 20 days, or even 35 days. In Turpan, there was an extreme heat of 47.8 °C, and the high temperature lasted for 39 days that year, close to a Grand Slam.
So will the ancient three-volt sky be so hot? From the historical data, the hottest summer in history appeared in the 8th year of Qianlong, when the weather in North China such as Beijing-Tianjin-Hebei, Lujin and other regions was very hot, from the actual measured temperature of French missionaries, the temperature on July 20-25, 1743 was above 40 °C, and on the 25th, it was 44.4 °C, which shows how hot the weather was.
Many people wonder, why is it so hot on a three-volt day? In fact, since the ambush, the surface humidity at this time will usher in an increase, and with the accumulation of heat in the surface layer, its temperature will become higher and higher every day, and when the heat accumulated on the ground reaches the highest value, the temperature will be the hottest.
At the same time, the summer rain is more, the humidity is relatively large, and the specific heat capacity of the water is larger than the air, making the weather more stuffy. In July and August, the subtropical high pressure is relatively strong, and the sinking air flow within the high pressure will drive the weather to be clear, and the sun will directly hit the ground, resulting in radiation heating up the surface, resulting in extremely hot weather.
Of course, as for when the "three-volt day" is the hottest, the first volt, the middle volt or the last volt, or whether there will be an "autumn tiger" after the last volt, it mainly depends on the specific weather conditions of that year, but the hottest weather in China is concentrated in the first volt and the middle volt, while the hottest weather in the southeast coastal area is at the end of the volt, and the middle and lower reaches of the Yangtze River are the hottest in the middle volt, and the "autumn tiger" also appears in this area.
After the arrival of the three volt days every year, many people's appetite weakens, at this time the weather is relatively dry and hot, everyone's appetite declines, many places pay attention to the eating habits of the volt, such as "head fu dumplings in the noodles", this is not a superstition, scientific research found that because the wheat has just harvested, eat new noodles more nutritious, and increase sweating and disease removal, and dumplings as delicious food, can be a good relief.
However, some people want to take a bath with cold water as soon as they arrive at three volts, or drink cold drinks, blow air conditioners for a long time, etc., which will lead to an increase in cold. Experts suggest that after the ambush, more ventilation, air conditioning can be 26 ° C, and morning and evening as far as possible to exercise, let yourself sweat, and after exercise in time to replenish water, eat less cool things.
At the time of the three volt days, there are many folk sayings, these old sayings are mostly a summary of life experience, let's take a look at the following sayings.
The so-called "Fu Bao Qiu" is the day of Li Qiu just the beginning of the last volt, which means that the day of Li Qiu is Geng Day; and if it is "Qiu Bao Fu", that is, first usher in Li Qiu, followed by the last volt weather, the difference is how many Volt days after Li Qiu.
If the autumn is relatively early, it means that there are still many futians, the autumn tigers continue for a long time, and everyone is "tortured" by the high temperature weather. The shorter the weather after the autumn, it means that the autumn tiger will not appear in a high probability, and it will not be long before it can enjoy the cool summer weather.
The last ambush of this year is August 10, and the autumn is August 7, indicating that this year is the "autumn package", which indicates that the temperature will continue to be high for a period of time after the autumn, the autumn tiger will also come, and the weather will be relatively hot.
The three volt days and the summer solstice festival have a lot to do with each other, after all, "the summer solstice three Geng into the head volt", so the folk will also judge the situation of the three volt days from the performance of the summer solstice. This saying is very simple to understand, if there is thunder on the day of the summer solstice, it means that there is more rain on the three-volt day, the duration of the rainy day is long, and the three-volt day is likely not to be high, as last year was so, the temperature is not too high.
If there is no rain on the day of the summer solstice, then the next three volt days are high in temperature and less rain, and everyone needs to pay attention to the heat prevention work, otherwise it may be heat stroke when farming outside.
When it comes to the three-volt day, it is a busy time for farming, and the crops at this time grow fast, and it is necessary to topdress and replenish fertilizer in time. In ancient times, it was mostly "male cultivators and female weavers", men were busy outside for a day, after returning, the body was dry and hot, and the rest environment was not good, the mood was not too good, and they might sprinkle the fire on the daughter-in-law, and as a result, there was a saying that "husband and wife turned their faces over".
In fact, from the weather forecast can also be seen, this year's three-volt day is relatively hot, the next temperature in the south will increase, and the minimum temperature will be above 26 ° C, the northwest due to dry weather, local areas will appear above 40 ° C temperature, so we should pay attention to good sunscreen.