Why does the east wind start in the middle of the night and the weather will be fine tomorrow?

It's an old saying that the east wind will start in the middle of the night and it will be fine tomorrow. According to relevant data, there was no weather forecast in the past, and our ancestors summarized the weather changes according to some natural phenomena. In rural areas, there are old agricultural proverbs who are familiar with this kind and are good at using it. People predict the change of weather according to the change of things around them, and identify sunny and rainy days. The east wind blows in the middle of the night, and it will be fine tomorrow. In the middle of the night, if the east wind blows, tomorrow will be sunny. Fog and dew in the south wind and frost in the north wind. If the south wind blows, it is easy to fog and dew; If the north wind blows, it will be very cold and easy to frost and snow.