Why does it snow every year in Harbin?

In winter, controlled by the continental cold air mass, the air is cold and dry, the solar radiation is weak, and the air is not easy to form violent convection, so thunderstorms rarely occur. But sometimes the weather is warmer in winter, and the power of warm and humid air is stronger. When the cold air in the north occasionally goes south, the warm and humid air is forced to rise, and the convection intensifies, so-called "thunder into winter" phenomenon will occur. Meteorologists also say that the occurrence of thunderstorms does not depend on the temperature itself, but on the upper and lower distribution of temperature. In other words, although the temperature is not high in winter, if the temperature difference between the upper and lower reaches a certain value, strong convection can also be formed, resulting in thunderstorms. Thundering in winter is rare in China, but it often happens in Toronto in winter.

When the air is extremely unstable, it is easy to have strong upward convection and form towering cumulonimbus clouds. Clouds are full of water vapor running up and down, which will generate static electricity. The upper end of the cloud will produce positive charge, the lower end of the cloud will produce negative charge, and the ground will be positively charged. Then, there is air as an insulator between the positive and negative charges. If the voltage difference between positive and negative charges is large enough to break through the air of the insulator, the air will instantly expand, explode, heat and glow.