What are the climatic characteristics of the first frost? What is the impact on agriculture?

The first frost, the first frost days in different parts of the country are quite different from north to south. For example, Changchun in the northeast has the first frost at the autumnal equinox, while Guangzhou in the south is generally rare. Even if there is, the first frost will not appear until the winter of the solstice. At this time, the daily average temperature in the middle reaches of the Yangtze River is between 14 degrees and 16 degrees, and the rainfall is between 20 mm and 30 mm. At this time, the cultivation management of rape and garden vegetables should be strengthened.