When does the day become shorter during the 24th solar term?

The 24th solar term begins after the autumnal equinox, and the days become shorter. The days in the Northern Hemisphere gradually become shorter. By the autumnal equinox, the days and nights in the Northern Hemisphere are the same. From the autumnal equinox, the days begin to be shorter than the nights. Until the winter solstice, the days in the Northern Hemisphere are the shortest. From the winter solstice, the days in the Northern Hemisphere begin to become longer. Until the spring equinox, day and night are the same.

This is because the heat near the ground is still accumulating at this time and has not reached its maximum. The summer solstice is the solar term with the highest rainfall in the entire year in the eastern part of the basin. In the future, it is often controlled by the subtropical high pressure and causes drought. In order to enhance drought resistance and achieve a bumper agricultural harvest, storing rainwater before drought is an important measure in these areas.

After the summer solstice, the ground is heated intensely and air convection is strong. Thunderstorms are often formed from afternoon to evening. This kind of hot thunderstorm comes and goes quickly, and the rainfall range is small. People call it "summer rain across Tiankan".

Liu Yuxi, a poet of the Tang Dynasty, cleverly used this kind of weather metaphor when he was in Sichuan and wrote the famous poem "The sun rises in the east and rains in the west, but there is sunshine in the road".