Why was the thunderstorm black the day before yesterday?

This is caused by the violent conflict between cold and warm air. The reason why it was dark the day before the thunderstorm was because of the fierce conflict between cold and warm air, which prompted the warm and humid air to rise. A large number of clouds blocked the sun, which would lead to a dark sky and heavy rain. Stay away from exposed metal objects such as water pipes, gas pipes and power equipment in thunderstorm days. It is not advisable to avoid thunderstorms under big trees or stay on high-rise platforms.