Why did it hail in Shanghai yesterday?

First of all, hail must have formed in convective clouds. When the water vapor in the air rises with the airflow, the higher the height and the lower the temperature, the water vapor will condense into liquid water droplets. If the height increases and the temperature drops below zero degrees Celsius, water droplets will condense into solid ice particles.

In the process of rising with the airflow, ice particles will absorb small ice particles or water droplets nearby and gradually become bigger and heavier. When the updraft can't bear its weight, ice particles will fall, but at this time the ice particles are not big enough. If you can meet a stronger updraft at this time and push the falling ice particles up again, the ice particles will continue to absorb small water droplets and condense into ice.

Under the adsorption and condensation of repeated ups and downs, ice particles will become bigger and bigger. When the ice particles grow big and heavy enough and there is not enough updraft to push them up again, they will fall to the ground. If the ice particles are still solid when they reach the ground, they are called hail. If they melt into water and fall, they become rain. Therefore, if the air is warm and humid, with sufficient moisture and strong convection, it is possible to produce hail.

Some hail is as soft as snow, but some hail is as hard as ice. If the hail is too large, it may cause damage to crops, buildings and even people. Therefore, when people see the hail from the sky, in addition to surprises, it is best to be careful of their own safety.