Which of the following two are the "two cold" weather in agricultural meteorological disasters in Guangxi?

The cold in late spring is mainly caused by long-term rainy weather or frequent invasion of cold air, or by strong radiation cooling on sunny nights under the control of cold anticyclone.

If the average temperature in late spring is more than 2℃ lower than normal, it is considered as cold weather in late spring, which can cause harm to agricultural production, especially in the early stage of late spring, which is higher than normal, and in the later stage, the temperature is lower. It can often cause rotten seedlings of early rice in southern China and rotten seeds or dead seedlings of peanuts, vegetables, cotton and wheat in northern China. In order to prevent late spring cold, we should not only improve the cultivation management level and raise seedlings by heat preservation, but also determine the reasonable sowing date according to the occurrence law of late spring cold in various places to avoid its harm. Simply put, in spring, the weather gets warmer, and the temperature drops obviously due to the invasion of cold air, which is harmful to crops. This kind of "warm before spring, cold after spring" weather is called late spring cold.

Late spring cold is a common weather phenomenon, not only in China, but also in Japan, North Korea, India and the United States. The reason is not complicated. Spring (March-April) in China is a transitional period between winter wind and summer monsoon. During this period, there are often intermittent cold air attacks from the northwest, and the cold air goes south and sticks to the warm and humid air in the south, resulting in continuous low temperature and rainy weather. Generally speaking, when the ten-day average temperature is more than 2℃ lower than normal, there will be more serious late spring cold. The later the cold air goes south, the stronger it becomes, the wider the cooling range, and the greater the possibility of cold in spring.

As the saying goes, "A child's face changes three times a day in spring." This is the climate in spring. Spring is a season with changeable climate. Although spring is getting warmer, it is still cold in the morning and evening, and the number of cold air activities is also frequent. In some years, there will be obvious late spring chill. If you take off your cotton-padded clothes too early, once the cold air strikes, you may not be able to adapt at once, and your body's resistance will drop, making you easy to catch a cold or even have a fever. Especially for the elderly with weak constitution and children with weak resistance, we should wear more clothes to avoid catching a cold and causing diseases.