How do dark clouds form?

In summer, surface water evaporates rapidly under the scorching sun, making the air humidity higher and higher; The temperature at high altitude is lower than the surface temperature, so the water vapor first reaches saturation and supersaturation at high altitude; There will always be some dust in the sky, which will become the condensation center, so that saturated steam and supersaturated steam will condense into fine water droplets.

When the fog drops are dense enough, they become white clouds visible to the naked eye; As the fog drops get bigger and bigger, the white clouds turn into dark clouds; The water droplets in the dark clouds continue to get bigger and become raindrops.

Extended data:

Long-term observation and practice show that the generation and dissipation of clouds, as well as the evolution and transformation between various clouds, are carried out under certain water vapor conditions and atmospheric movement conditions. People can't see water vapor or atmospheric movement, but we can see every move of water vapor and atmospheric movement from the evolution of clouds, and water vapor and atmospheric movement play an extremely important role in weather phenomena such as rain, snow, freezing hail.

For thousands of years, the working people in our country have summed up the rich experience of "knowing the sky by observing the clouds" according to the changes in the shape, direction, moving speed, thickness and color of clouds in production practice, and compiled these experiences into proverbs.

Baidu Encyclopedia-Dark Cloud