What kind of weather conditions must rainfall have?

If there is rain, there must be clouds first, and if there are clouds, there must be rain. There are several conditions to produce rainfall: first, there must be water vapor conditions. The second condition is that there must be upward movement, which is equivalent to the processing process. Because upward movement brings water vapor to high altitude and condenses to form clouds, it can produce precipitation, so upward movement is essential. The third condition is an appropriate amount of condensation nuclei, because water vapor condensation needs to be attached. Without condensation nuclei, water vapor cannot condense effectively. If there are not enough ice crystals in this cloud in nature, because the water droplets in the cloud are very small and can be suspended in the air for a long time, then only the cloud has no rain. At this time, if silver iodide particles are sown in this cloud, many ice crystals will be produced, and the water on the water droplets in the cloud will be quickly transformed into these artificial ice crystals through evaporation and condensation, which will make the ice crystals grow rapidly and produce snowfall. If the ground temperature is high, it will snow.