Rain forms and gets into clouds through water vapor that turns into clouds when it cools and condenses.
Water turns into vapor as the water evaporates such as from lakes, streams, surfaces etc then the water vapor rises into the air and becomes droplets in a cloud.
When the clouds get too full of those water droplets they release the water droplets as rain which can be a heavy downpour or drizzle.
The heat causes water vapor to rise up from the ground.
As it rises, it cools and condenses into droplets.
These droplets are what we call rain clouds.
Rain clouds can also form when a plane or ship releases water vapor into the air.
The rain cycle is pretty simple.
Bodies of water evaporate under the warmth of the sun, turning from liquid to gas.
That warm gas rises up into the sky. But as it rises, it hits cooler air and as it cools, it turns liquid again.
At first, these water droplets are very small.
As the air rises, it expands and cools.
This phenomenon is called condensation.
The condensation of water vapor results in the formation of clouds.
These clouds are carried away with the help of wind and when they become heavy they fall down in the form of rain.