Is frost really the cold air in the weather forecast?

Of course it is true, and there is evidence! First, we must understand how frost is formed:

The formation of frost is not only related to the weather conditions at that time. When the temperature of the surface of an object is very low, but the temperature of the air near the surface of the object is relatively high, there is a temperature difference between the air and the surface of the object. When the warmer air comes into contact with the colder surface of the object, the air will cool. Excess water vapor in the air will precipitate. If the temperature is below 0°C, excess water vapor condenses into ice crystals on the surface of the object, which is frost.

In addition, clouds hinder the radiative cooling of ground objects at night. Clouds in the sky are not conducive to the formation of frost. Therefore, frost mostly appears on clear nights, when ground radiative cooling is intense.

In addition, wind also has an impact on the formation of frost. When there is a breeze, the air slowly flows across the surface of cold objects, continuously supplying water vapor, which is conducive to the formation of frost. However, when the wind is strong, the air flows very fast and the time it touches the surface of cold objects is too short. At the same time, when the wind is strong, the air in the upper and lower layers easily mix with each other, which is not conducive to lowering the temperature, which will also hinder the formation of frost. Generally speaking, when the wind speed reaches level 3 or above, frost will not easily form.

When straw is burned in the fields at night when frost is prone to occur, it increases the temperature near the surface and accelerates the flow of air near the surface. The smoke formed by burning reduces the ground radiation cooling and destroys the conditions for frost formation. Frost is less likely to occur.