How are Ice Crystals formed?
Droplets of liquid condensation from the rain clouds freezes, thus forming ice. They create a crystalline structure. The air from the ground pushes itself upwards and carries the moist, warmer air into the colder parts of the atmosphere. This helps to begin condensation high up where rain clouds are formed. Snow forms above the rain clouds.
What makes the Ice Crystals fall?
When condensation happens; the water freezes to form ice crystals. These small ice balls pass through additional clouds and become heavier. Thus they fall onto the ground as they are too heavy to stay up.
If the air is still the water is in the form of vapour and as the temperature falls molecules of water come together and form crystals. If the air is freezing cold all the way to the ground then these crystals fall as snowflakes.