There are many dark clouds in the sky. It looks like rain. Why didn't it rain after waiting for a long time?

This phenomenon is caused by two reasons. On a summer morning, there is a common cloud with a round top and a flat bottom, isolated in the air. It is called light cumulus cloud (commonly known as steamed bread cloud). Around noon, this faint cumulus gradually developed into a thick cloud with the top like cauliflower, which is called thick cumulus. At this time, it seems that the dark clouds are reunited again. In fact, this kind of cloud usually doesn't rain, only a little rain at most. When it further develops into a cumulonimbus cloud, it seems that the top of the cloud is no longer like a cumulonimbus cloud, but it is going to rain. In addition, sometimes when the cumulonimbus cloud moves closer to the local area, there is a strong updraft at the front edge, which causes the black cloud to roll. Although this rolling cloud is fierce, it usually doesn't rain; When the dark clouds cleared, violent showers followed. Therefore, it caused the phenomenon that the dark clouds gathered without rain, but dispersed and then rained. The weather proverb circulating in rural areas: aconite wind, bald rain, also means this.