There is a saying that "it is better to open a river by two feet than to seal a river by one inch", that is to say, although the ice in winter is thin, it is more flexible. At that time, although there was a sound of ice cracking when walking on it, it generally wouldn't break, but once it broke, it would collapse into the water in a large area, so it would be safe if the thickness of the river reached 2 cm in winter, and the small pond would be fine even if it was 1 cm. The second half says that the ice is brittle when it is civilized in spring. Although it looks thick, it is not flexible. It is very likely that one foot is on the ice and the other foot will step into the water. It was more dangerous at that time, so the ice in spring could not go. I come from Heilongjiang, and these are my own experiences. For the sake of safety, it is best not to skate in the river. If you want to experience nature, it's the middle of winter. For example, you can drive on the ice of any river in Heilongjiang this season.