How many degrees below zero will it snow?

When the temperature is between -8℃ and -5℃, prismatic ice crystals will form and it will snow. However, the formation of snowfall must meet two conditions:

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.

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.