It freezes at MINUS several degrees.

Generally speaking, ice will not freeze at 20 degrees Celsius. Zero degree is the freezing point. No impurities will freeze at 0 degrees, and some impurities will freeze below 0 degrees, about 3 degrees below zero.

Road Icing

Road icing is easy to occur from June 1 1 to April of the following year (that is, winter and early spring). Road icing often occurs in northern China, especially in the northeast and northern Inner Mongolia. In southern China, snowfall is generally "wet snow", which often belongs to mixed water of 0 ~ 4℃. When it falls to the ground, it will turn into ice water paste, and when the temperature drops at night, it will solidify into large ice cubes.

As long as the local minimum temperature is below 0℃ in winter, road icing may occur, and as long as the temperature does not rise enough to melt the ice, it will remain as solid as a rock. Generally speaking, in the cold winter, when the temperature drops due to a wide range of strong cold air activities (called cold wave in meteorology), if it is accompanied by rain and snow, it is most prone to road icing.

In winter, the temperature drops suddenly, and sometimes there will be a layer of frost or thin ice on the brake disc, which will seriously cause the brake calipers to fail to close. So when driving in snowy days, be sure to check the brake system. After the vehicle starts, you should lightly step on the brakes and check whether the brakes are normal, so as to avoid being caught off guard when there is a problem.