Rain happens when water droplets inside clouds grow large and heavy enough to fall to the ground. Rain can be light (a drizzle) or heavy (a downpour). Rain is important because it gives water to plants, fills rivers and lakes, and provides drinking water. After rain, you can see puddles, wet ground, and sometimes rainbows.
Let children observe rain from a safe covered area. Place cups outside to collect rainwater and compare amounts. Discuss what happens before, during, and after rain -- how the sky looks, how the air smells, where puddles form. Read stories about rainy days and connect them to real observations.
You already know that clouds are made of tiny water droplets floating in the air. So where does rain come from? Rain happens when those tiny droplets grow bigger. Inside a cloud, the little droplets bump into each other and stick together. As they join up, they get larger and heavier. Eventually, a droplet gets so heavy that the air cannot hold it up anymore, and it falls to the ground. That falling water is rain.
Not all rain is the same. Sometimes rain is very light -- just a fine mist or drizzle that barely gets you wet. Other times, rain is heavy, with big drops falling fast and soaking everything quickly. Heavy rain usually comes from big, dark clouds, while light rain might come from thinner gray clouds. The darkness of a rain cloud tells you something: darker clouds are thicker and hold more water.
Rain is one of the most important things that happens on Earth. Plants need rain to grow -- their roots drink water from the soil, and rain is what puts that water there. Rivers and lakes are filled by rain. The water you drink, the water farmers use to grow food, and the water that animals depend on all originally fell from the sky as rain. Without rain, the land would become a desert.
After a rainstorm, look around. You will see puddles on flat surfaces where water collected. You will see wet sidewalks and dripping leaves. The air might smell fresh and earthy -- that smell comes from the rain hitting the soil and releasing scents from the ground. And if the sun comes out while rain is still falling, you might see a rainbow -- sunlight bending through the raindrops and splitting into colors.