When the temperatures are cold there may be frost, snow, sleet, or hail. When it is cold water will turn into a solid called ice. When it is humid dew will form on plants and other things. Humidity is when the air is moist, or has lots of water in it water can also evaporate, or turn into a gas. If a lot of water turns into gas it is humid.
Rain is water that falls from clouds.
A cloud is made of water. When a cloud gets heavy it will drop water. Snow is frozen rain. All water is made of billions and billions of water molecules. Molecule are microscopic.