How many degrees can it snow?

There are two conditions for the formation of snowfall:

One condition is that water vapor is saturated. Another condition is that there must be condensation nuclei in the air.

The size of snowflake crystals is closely related to the temperature at which water vapor condenses and crystallizes. The colder the weather, the lower the temperature and the smaller the snowflake crystal. When the weather is very cold, the diameter of snowflake crystals formed is often less than 0.05 mm. Meteorologists have observed that prismatic ice crystals will form when the temperature is between -8℃ and -5℃.

When the temperature is -5℃ to -3℃, needle-like ice crystals are formed; When the temperature is -3℃ to 0℃, thin hexagonal plate-like ice crystals are formed. It can be seen that when the temperature is -3℃ to 0℃, the shape of snowflake is the largest and most complete. Snowflake crystals formed in very cold weather are so small that they are almost invisible to the naked eye. Only when they shine in the sun can people find them as fine powder. This kind of snow is called dry snow.

Extended data:

Snow, like rain, is formed by the cooling and condensation of water vapor in the air, but the degree of cold weather is different when it is condensed, so there is a difference between rain and snow. When the temperature in the upper layer of the sky is very low and the water vapor in the air condenses, it is not condensed into water droplets, but directly condensed into small snowflakes by water vapor. This transformation from gas to solid without liquid is called sublimation in meteorology.

So it can be considered that snowflakes are ice formed in a special way. When there are ice crystals and supercooled water droplets in the cloud (water droplets can be retained in the cloud when the air flow in the cloud is stable and the temperature is -20 degrees Celsius or lower), it is easy to produce snowflakes. Supercooled water droplets evaporate more easily than ice crystals.

When the water vapor on the ice crystal is saturated and no longer evaporates, the supercooled water droplets do not stop evaporating at this time, and the evaporated water vapor sublimates and condenses on the surface of the ice crystal, and the volume gradually increases, becoming loose dendritic hexagonal small ice flowers, which is snow.

The shape of snow is very beautiful, the pattern is very neat, the structure is complex and the shapes are diverse. More than 4000 different patterns have been found. Some of them are like blooming peony, some are like thin plum blossoms, some are like antlers with branches, and some are like frozen ice flowers on the glass. If you put them together, you can form a beautiful pattern.

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