What is the weather sign of frost?

A common agrometeorological disaster refers to the sudden drop of temperature, and the sudden drop of surface temperature below 0℃, which damages crops and even kills them. Generally appear in autumn, winter and spring. It's different from frost. Frost is a white ice crystal that condenses directly on objects when the water vapor in the air near the ground reaches saturation and the ground temperature is lower than 0℃. When there is frost, it is not necessarily frost.

Extended data:

Generally speaking, the first frost appears in autumn and the last frost appears in spring. However, China has a vast territory and complex terrain, and the climate varies greatly from place to place. Therefore, the distribution of frost period and the first and last frost days is different from place to place. The first frost appeared gradually from north to south and from mountainous area to plain in China.

Among them, the first frost in Northeast China, Daxing 'anling and Xiaoxing 'anling areas appeared before mid-September. 10 From mid-September to mid-June, the first frost began to appear in the southeast of Northeast China, central Inner Mongolia and North China.

The first frost gradually began to appear in the Yangtze River basin (from mid-June 65438 to mid-June 65438+June 065438+10). However, the first frost did not appear in the Sichuan Basin in the upper reaches of the Yangtze River until 65438+February, which was nearly 12 months later than the surrounding areas, which may be related to the special topography of the Sichuan Basin.