Clouds blocked the dam for three days in the morning, indicating rain.

Clouds block the dam in the morning, and it usually rains within three days. Cloud dam is a weather phenomenon, which shows that there is a narrow cloud belt on the weather map in the morning, which spans some areas and has a clear belt parallel to it along its southern edge. The cloud dam is formed because the wind direction at the southern edge of the high-pressure system has changed during the vertical development. When the wind blows from the southern edge of the high-pressure system to the cloud dam, the cloud belt will move northward, forming an updraft inside the cloud belt, which will lead to rainfall. So if there is a cloud blocking the dam in the morning, it is likely to rain within three days.