The maximum temperature difference between day and night in autumn and winter has arrived.

The biggest temperature difference between day and night in autumn and winter is the solar term of first frost.

The first frost period, the last solar term in autumn, is also the solar term with the largest temperature difference between day and night in most autumn and winter seasons in China. At this time, cold air frequently affects China, and the temperature fluctuates greatly. Let's take a look at the map of the country's disorderly dressing, and see where it changes two seasons a day, and the pace of dressing is chaotic.

The first frost, there are two seasons in the north. During the frosty solar term at the beginning of the year, the temperature difference between day and night in central and southern Xinjiang, Ningxia, northern Qinghai, northwestern Shaanxi, southwestern Shanxi, western Sichuan and parts of Tibet can exceed 65438 05℃, and there are two seasons in one day.

Cold air often patronizes these areas, and the temperature fluctuates greatly. Coupled with the high altitude, the heat is lost quickly at night, so it is enough to wear light clothes during the day, but winter clothes such as thick coats and cotton-padded jackets are needed to keep warm in the morning and evening.

Agricultural activities during the first frost

After the first frost solar terms, cold air activities become more frequent, and the temperature difference between day and night becomes larger. The "first frost" solar term has nothing to do with "first frost", which does not mean that entering the first frost solar term will lead to "first frost". In fact, "frost" does not fall from the sky, but the water vapor on the ground condenses when it meets cold air due to temperature difference changes.

There is no concept of "first frost" in meteorology. Generally speaking, the first frost in autumn is called "first frost" or "first frost", and the last frost in spring is called "late frost" or "final frost". The interval from the last frost to the first frost is a frost-free period. In the first frost season, most parts of the north have been harvested in autumn.

Even cold-resistant onions can't grow any longer, because "the first frost can't support onions, and the longer they grow, the more empty they are." In the south, it is the peak season of "Sanqiu". Only single-season hybrid rice and late rice are harvested, and early-season wheat and early-season rape are planted. Picking cotton, pulling cotton stalks, ploughing and soil preparation.