Why does it snow in cold weather and hail in warm weather?

In warm weather, hail can form in convective clouds, while in cold weather, the temperature is lower, because the water vapor in the air condenses directly and forms snow.

The area with the most hail in China is the Qinghai-Tibet Plateau, such as Heihe (Naqu) in the northeast of Xizang Autonomous Region, with an average annual hail of 35.9 days (53 days in the most years, at least 23 days); Followed by Bango 3 1.4 days, Shenzha 28.0 days, Amdo 27.9 days, Suoxian 27.6 days, all appeared in the Qinghai-Tibet Plateau. Generally speaking, the time distribution of hail disasters in China is very extensive. Although there is hail at any time of the day, there is a relatively concentrated hail period all over the country.

Snowflakes are mostly hexagonal, and there are so many patterns because the molecules of ice are mostly hexagonal. For hexagonal flake ice crystals, because of their different curvatures on the surface and edges, they have different saturated vapor pressures, of which the saturated vapor pressure on the edges is the largest and the edge on the plane is the smallest.