What is the weather symbol for frost?

The weather symbol of frost is:

A relatively common agricultural meteorological disaster refers to a sudden drop in air temperature and a sudden drop in surface temperature below 0°C, causing damage to crops. Even death. Usually appears in autumn, winter and spring. It is different from frost. Frost is white ice crystals that condense directly on objects when the water vapor in the air near the ground reaches saturation and the ground temperature is lower than 0°C. When there is frost, it is not necessarily frost.

Extended information:

Generally speaking, the first frost appears in autumn and the last frost appears in spring. However, our country has a vast territory, complex terrain, and the climate varies greatly between regions. Therefore, the frost period in various regions The distribution of first and last frost days is also different. The first frost in various parts of China generally appears gradually from north to south and from mountains to plains.

The first frost appears before mid-September in the northern Northeast, Daxinganling and Xiaoxinganling areas. From mid-September to mid-October, the first frost begins to appear in the southern part of Northeast China, central Inner Mongolia, and North China.

The first frost gradually begins to appear in the Yangtze River Basin (from mid-October to mid-to-late November). In the Sichuan Basin in the upper reaches of the Yangtze River, the first frost did not appear until December, nearly 12 months later than surrounding areas. This may be related to the special terrain of the Sichuan Basin.