What do you mean by thunder in beginning of spring?

The thunder in beginning of spring refers to the thunder on the day of the solar term in beginning of spring.

As the saying goes in the countryside, "When it thunders in beginning of spring, there are nine vacancies in ten pigsty". The thunder in beginning of spring refers to the lightning and thunder in beginning of spring that day. Generally speaking, thunder is rare in spring, but it is even rarer in beginning of spring that day. Therefore, if you hear thunder on the day when the spring solar term begins, farmers can predict the harvest of crops and raise pigs at home.

The thunder of solar terms in beginning of spring shows that the warm air is very strong at this time, and the temperature will rise rapidly at this time. The cold air may be temporarily suppressed by the warm air, but it will come back in the cold winter after all, which is what we often call the cold weather in spring. The arrival of cold weather in late spring has caused freezing damage to farmers, and the temperature in spring is low, so many crops can't be sown on time, resulting in reduced grain production or poor harvest. There are nine empty pigsty in ten places, which clearly tells us that the pigsty in farmers' homes is basically empty and farmers don't raise pigs. The reason why farmers don't raise pigs is mainly because there is no surplus grain to feed pigs. Farmers can raise pigs because there is surplus grain in the harvest year, so the surplus grain can be used to feed pigs. Therefore, every family raises pigs in good years, and there are nine empty pigsty in good years.