What does the phrase "Yun Qi flowers in the morning and people die in the afternoon" mean?

The clouds in the morning look faint, and it will be very hot at noon and afternoon. This is a folk proverb. Clouds bloom in the morning and fade in the afternoon. It's sunny in summer. The clouds referred to in these proverbs are all faint cumulus clouds in the clear sky. Why do light cumulus clouds symbolize sunny days? We must look at several situations that form light cumulus clouds.

It is cloudy in summer. If the weather is clear in summer morning, the ground will heat up rapidly due to the sun's irradiation, and the long-wave radiation after the ground is heated will also make the air temperature near the ground rise rapidly, so the air near the ground will expand and become lighter and rise. This is convection caused by thermal action. When the rising air mass cools to a certain extent during the rising process, the water vapor in the air will condense into clouds and generate light cumulus clouds. If the air stratification is unstable at this time, light cumulonimbus clouds can develop upward into light cumulonimbus clouds and cumulonimbus clouds. However, if the air stratification is very stable, the light cumulus cannot develop upward, thus forming a piece of lonely and divergent light cumulus, which floats in the air in disorder to form a scene of clouds in the sky. The light cumulus will definitely not rain, and the weather will naturally be fine.

Another reason for light cumulus clouds is the rise of fog during dissipation. Foggy weather is generally a symbol of good weather, but not the light cumulus clouds produced by this weather situation is naturally a symbol of good weather.

If what we see in the morning is a faint cumulus, and with the rising of the sun, the faint cumulus quickly develops into a thick cumulus, then the situation is different from that mentioned above, which is not necessarily a sign of good weather.