Why didn't it snow this winter?

In winter, if it snows, two conditions must be met to form snowfall:

One condition is that water vapor is saturated. The maximum amount of water vapor that air can hold at a certain temperature is called saturated water vapor. The temperature at which air reaches saturation is called dew point. When saturated air is cooled to a temperature below the dew point, the excess water vapor in the air becomes water droplets or ice crystals.

Another condition is that there must be condensation nuclei in the air. Some people have done experiments, if there is no condensation nucleus, the water vapor in the air will only condense into water droplets if it is supersaturated to a relative humidity of more than 500%. But such a large supersaturation phenomenon will not exist in the natural atmosphere. So without condensation nuclei, it is difficult for us to see rain and snow on the earth.

Extended data:

Matters needing attention when it snows

1, improper way to keep out the cold

Improper way to keep out the cold. Young people who like fashion must pay attention to changing clothes in time when they enter and leave the environment with large temperature difference between indoor and outdoor. On snowy days, in order to pursue fashion, you can't show your legs or wear thin clothes. At the same time, pay attention to a light diet and don't eat too much cold food at a time to prevent acute gastroenteritis.

2. Prevent accidental falls.

Prevent accidental falls. Rain and snow make the road slippery. Therefore, the general public is specially reminded to pay attention to travel safety and prevent accidental falls.

3. Prevention of respiratory diseases

When the weather gets cold, the first thing to test is the respiratory system. Usually do not pay attention to exercise, coupled with the closed indoor air does not often circulate with the outside world, it is likely to cause upper respiratory tract infection.