One of the basic facts that preschool children may ask is a very simple one: What is rain? Try to explain that water always exists in the air, but when clouds contain a large amount of water, that water forms together in droplets and falls to earth. Gauge your class's ability level and adjust the information accordingly, you may wish to provide more detail or specific information about gravity or the measurements of the average rain drop. Websites such as Weatherwizkids.com will help.
The rain cycle is the process of rain falling to earth, running off into rivers and streams and returning to clouds through evaporation. Teaching this process to preschool children might get a little boring, so consider developing a song about the cycle by changing the words of a well-known children's song such as "London Bridge" include movements to illustrate the cycle. This will get the students up on their feet, and help them remember the information later on.
You may not wish to alarm preschool age children, but if there has been heavy flooding in your area, you may find it useful to explain the process to your students. Flooding usually occurs after several days of heavy rain. The water levels in rivers and stream rise and overflow the banks. This can cause damage and destruction. Make sure you teach your students some good tips for surviving a flood, such as moving to higher ground, avoiding tap water and never playing areas with high water.
Teaching kids about acid rain, is a great way to teach them about how humanity has affected the environment. Acid rain occurs because of the burning of fossil fuels. Dangerous chemicals combine with water in the atmosphere and fall to earth as Acid rain. This rain has a number of negative effects on aquatic creatures which can die when exposed to poisonous levels of acid in the water. Animals that these aquatic creatures are also subsequently poisoned. Use pictures to illustrate the food chain and show how this process even affects human beings.