What are the rules all year round?

Take the average temperature as the temperature index to divide the four seasons. Summer begins when the average climate temperature is stable above 22℃, winter begins when the average climate temperature is stable below 10℃, and spring and autumn begins when the average climate temperature is between 10 ~ 22℃. 10℃ to 22℃ is spring, and 22℃ to 10℃ is autumn.

Generally, it is divided by provinces.

Four seasons refer to four seasons that appear alternately in a year, namely spring, summer, autumn and winter, and each season lasts for three months. All the year round is formed because the earth revolves around the sun. Due to the existence of the ecliptic angle, the direct point of the sun moves back and forth between the north and south latitudes of the earth, resulting in annual variation.

In this way, the height of the sun at noon and the length of day and night change seasonally, and the amount of solar energy obtained by various places changes seasonally, thus forming the replacement of four seasons.

In ancient times, the direction of bucket handle determined the alternation of seasons and the rotation of the Big Dipper, which was closely related to the change of seasons. At present, the division of seasons is usually determined by the position of the earth in the orbit around the sun. The rotation of the four seasons reflects the changing laws of phenology and climate such as spring, long summer, autumn harvest and winter storage.

There are many rains, heavy rains and sunny days in southern China (low latitudes), and the changes of rainfall, heavy rains and sunshine are obvious when the seasons change. There is little rain and storm in the northern region (mid-latitude region), and the temperature changes obviously when the seasons change.

Spring ranks first among the four seasons, and a new cycle begins. Spring represents warmth, growth, plant germination, warm weather and flowers. The temperature, sunshine and rainfall in this season are at the turning point of the year, and there is a rising or increasing trend.

In spring, the qi of yin and yang begins to change, and everything germinates and grows with the rise of yang. Spring is the season for all things to grow and sow. The so-called "one year's plan lies in spring".

Everything is thriving in summer, which is the peak season for crop growth. The temperature rises, the weather is hot, storms are frequent, and everything flourishes. Summer is the most stormy season, often accompanied by strong winds and heavy rains. In the northern hemisphere summer, the continental heating pressure rises to form a low pressure, and the ocean constant temperature is relatively low to form a high pressure. According to the circulation, the southeast wind blows in summer. In summer, the days are the longest in all parts of the northern hemisphere.

Autumn is the harvest season, which means that everything begins to mature from lush. In the first two solar terms in autumn, beginning of autumn is in summer, and the weather is still very hot. Because the heat brought by the sun has not weakened, the so-called "heat is in the dog days." The dog days appear between midsummer and hot summer, which is the highest, wettest and sultry day of the year. The reason for the high humidity in dog days is that the southeast wind blows in dog days, and the southeast direction is the Pacific Ocean and the Indian Ocean, so the air is humid, and the humidity of the wind causes the high humidity in dog days. After late autumn, the opposite is true. The northwest wind blows and the northwest inland is dry. The dry northwest wind leads to a dry climate after late autumn. The climate characteristics of the first two solar terms in autumn are humid and sultry. Generally, it is really cold in autumn, until after the solar term of the Millennium, it gradually tends to be cool and dry from the Millennium. In late autumn, the climate turns from hot to cold, and everything comes into being with cold and gradually falls. This is the season of alternating hot and cold. The most obvious change in autumn is that the leaves of vegetation change from lush green to yellow, leaves begin to fall and crops begin to mature.

In winter, yin and yang change, everything is hidden but not collected, and plants are angry and closed. After entering beginning of winter, it means that the dry climate with little rain in autumn has gradually passed and turned into a rainy and cold winter climate. The height of the sun in the northern hemisphere is small and the days are short. The so-called "dog days are hot", the cold is on March 9, and the solstice in winter is "September 19". It was not too cold before the winter solstice. After the winter solstice, strong cold air frequently goes south and crosses Nanling, and the temperature drops sharply and the weather is cold. Winter is really cold, the solstice after winter.