Rain is part of a continuous loop called the water cycle, where water travels from the ground to the sky and back again. This process involves water changing its form and moving through the atmosphere.
The Water’s Journey Begins
The sun starts the water cycle by acting as a heater for the planet. When the sun shines on water in oceans, lakes, and soil, it warms the water. This heat gives water molecules enough energy to break away from the liquid and float up into the air as an invisible gas called water vapor.
Water vapor is lighter than the surrounding air, allowing it to easily lift and begin its journey high above the ground. As the vapor travels higher in the atmosphere, the air pressure and temperature drop. This cooling is the first step toward forming a cloud.
Making Clouds
When warm, moist air reaches colder temperatures high in the sky, the water vapor begins to turn back into tiny liquid water droplets. This transformation from an invisible gas back into a visible liquid is called condensation.
The water vapor needs a tiny surface to stick to before forming droplets. Millions of microscopic particles, such as dust, pollen, or salt crystals, float in the air and act as seeds for the water droplets to collect around.
Billions of these microscopic water droplets and ice crystals cling together, forming clouds. A cloud is a collection of these tiny water particles suspended in the air. These droplets are so small and light that air currents keep them floating, preventing them from falling immediately.
How Rain Drops Fall
The cloud continues to gather water vapor, causing the tiny droplets inside to bump into each other as they float. When these droplets collide, they stick together and merge, gradually becoming larger and heavier.
This growth continues until the water drops become too large for the air currents to hold them up. Once a drop reaches a certain size, the force of gravity pulling it down becomes stronger than the air pushing it up.
The heavy water drops then fall back to Earth as rain. This falling of water from the sky is called precipitation. The rain collects in rivers and lakes or soaks into the ground, ready for the sun to start the entire journey over again.