Science Facts

How Rain Is Formed? – Water Cycle, Cloud & Rainfall Types

Rain Formation

Water can exist in three states like solid, liquid, and gas. When we want to get ice from water, we put the water in the freezer, cool the temperature down, and get ice. So how do we get water from gas? Well, We use the same process. We need to take the water vapor and cool the temperature down and bring water. This is how clouds are created, which eventually leads to rain.

The sun’s heat evaporates water from rivers, lakes, oceans, or even plants placed in the ground. It creates water vapor or water in the form of gas rising in the air. As the water vapors rise in the air, the surrounding temperature cools, turning the vapor into water droplets.

The air is filled with dust, and these water droplets collide with the dust forming the clouds in our sky. When this process happens repeatedly, our cloud gets bigger, and water droplets collide together, making them heavier and heavier. Once the water droplets in the clouds are heavy enough, gravity takes over, and the water droplets fall onto the earth. In other words, it rains!

How rain is formed?

In the summer, it’s hot, and water vapor remains as a gas, leading to fewer water droplets in the clouds that are heavy enough to fall as rain. Did you know? When you combine all the colors in the world, you get the color white. That’s what light coming from the sun is: a combination of all the existing colors. And that’s the reason the clouds are white. They are reflecting the light coming from the sun. Before learning rain formation, we need to understand the water cycle.

Water cycle explanation

The water cycle has a few main parts. They include:

  • Evaporation.
  • Condensation
  • Precipitation.
  • Collection.

Now we will discuss the water cycle step by step process.

Water cycle diagram

Step 1 – Evaporation: What sources of water are available for evaporation? This is where water turns from a liquid to gas. Example: From a puddle to a pond, pond to a lake, lakes to rivers, and rivers to seize.

The water is turned into a vapor and goes into the air. An unusual source of water comes from plants. Plants transpire essentially. This means lose water from their leaves similarly and or sweat or perspire. All of these processes cause water to evaporate.

Step 2 – Condensation: Once the water has entered the atmosphere, what do you think happens? The water vapor will start to condense because of the low temperature of the atmosphere. When it does this, it forms clouds.

Step 3 – Precipitation: Once all of the water is collected in the cloud, what happens next. It falls back down. A fancy word for this is precipitation. And it can take many forms, including rain and snow. Precipitation is the process of water falling onto the surface of the Earth.

Rain is falling water in liquid form. Snow, ice, hail, and sleet are falling water in solid or frozen form. Precipitation that falls directly into the oceans becomes part of the surface ocean and can be churned by wave and wind action into ocean currents. Rain and snow that fall directly on rivers and streams become one part of streamflow. Also, The rain that falls onto land takes a different path to the river.

Step 4 – Collection: Finally, the water is collected on land by rainfall. It either soaks back into the earth, becoming groundwater from which plants and animals can drink. It may run over the soil collecting in lakes, oceans, and rivers where the water cycle then repeats.

How does rain form in clouds?

When seawater from big ocean waves gets blown up into the air, some of it can evaporate, leaving behind a particle of sea salt just suspended in the air. That speck of sea salt makes the perfect condensation nuclei. So why don’t we throw all these rainmaking particles over the areas that need rain the most, like dry farmlands? It’s called cloud seeding.

Raindrops aren’t as crystal clear as they seem. They’re a little dirty. Microscopic dirt particles from the earth get blown high into the atmosphere. When they get up there turns out they are just the perfect thing for water vapor to condense. When water is a vapor, the individual molecules move so quickly and so erratically. They find it hard to light up just the right way to form bonds and turn into a liquid. Instead, they find it much easier to condense onto one of these microscopic particles.

It’s called a cloud condensation nucleus to make a cloud. You need lots of these tiny little rain droplets, which means you need many nuclei to get things started. When you have enough of them, that’s a cloud. And more and more rain droplets and the cloud can get larger and larger. When there’s enough of them, they start bumping into each other faster than they can evaporate. It makes raindrops that can grow larger and larger until they’re big enough to survive the fall down to the earth.

Raindrops are good trillions of these particles in the atmosphere. They’re things like dust, dirt, pollen pollution, pollen fragments, mushroom spores, even bacteria. Some scientists think that some types of bacteria and mushroom spores may have evolved to be the perfect cloud condensation nuclei so that they can build a raindrop around them to help them get back down to earth.

One kilometer-wide hypothetical cloud contains a volume of 1 billion cubic meters of water or raindrops. With some basic arithmetic, the cloud holds 250 metric tons of water! Strom clouds are huge for having a much higher water density so much. Their average water content has been estimated at 50,000 metric tons. That’s enough water to fill 20 Olympic-sized swimming pools. Average cloudy droplet falls at naught point naught 3 kilometers per hour. It means it would take 33 hours to fall just 1 kilometer.

In the light updraft, tiny droplets are just heavy enough to fall gently to the ground. And this creates a hazy light kind of rain shower. But a stronger updraft keeps the water droplet up in the clouds for longer. So they have more time to bump into each other. They unite, coalesce and make bigger raindrops. Eventually, they become so big that the updraft can no longer support their weight. So they fall as giant raindrops or rainfall.

As they fall, a turbulent gust of air can blow them back up into the cloud, where they bounce around into even more raindrops and get even bigger. The longer a raindrop falls, the more likely it will get blown back up into a cloud or another drop.

Types of rainfall

Rain is water from the sky, but not all rain is created equal. There are three types of rainfall. Orographic, frontal, and convectional.

Orographic rainfall: Orographic precipitation is known as relief precipitation. It is most commonly found in coastal regions with a mountain range. Wind from the sea contains a lot of moisture, and when it reaches a mountain, it cannot continue and is forced upwards. As the air mass goes upwards, it cools and eventually condenses into clouds. Soon after, the cloud can no longer hold any more water, and it begins to rain.

Most precipitation ends up on the side facing the ocean, called the windward side, while the other, or leeward side, gets little. It causes one side to be moist and full of vegetation while the other is dry.

Frontal rainfall: Next, there is frontal or cyclonic precipitation. When a warm moist air mass meets a cold, dry one, the warm one rises, and the water vapor in the warm air condenses as it rises, forming clouds. Eventually, it will rain. If it is a warm front, the warm air will gradually rise to cause a mild to prolonged moderate rainfall.

If it is a cold front, the warm air will rise quickly, causing unstable weather, including thunderstorms. Frontal precipitation is widespread in the British Isles.

Convectional rainfall: The final type of rainfall is convectional precipitation. On hot days, the sun heats the ground. The ground then releases some of that heat which warms the air. That warm air rises and cools to condense its water vapor into a liquid. This causes rainfall to initiate almost instantly, usually without much warning. Since convectional precipitation relies on the sun upon heating the ground, it is far more common in tropical regions, where the sun hits more directly and intensely.

These three types of rainfall have ultimately shaped our society, providing the hydration necessary for vegetation to exist.

The Sun is beating down on tropical waters powers the weather systems of the globe. Moisture evaporates from the warming ocean and rises to create great storms. The whims generated out at sea sweep inland across the continent. As they travel across the Sahara, they make the biggest of all sandstorms. They are blowing sand halfway around the world to fertilize the Amazon jungle.

Wind blowing across the Indian Ocean collects moisture and sweeps northwards towards the Himalayas. As the air rises, so it cools. The water it carries condenses into clouds and then falls as the life-giving rains of the monsoon. So air currents powered by the Sun carry wet air to the middle of continents.

More Article:


Steve Kempler. “Parameter information page.” NASA Goddard Space Flight Center.
Mark Stoelinga. Atmospheric Thermodynamics. University of Washington.
Glossary of Meteorology. “Relative Humidity.” American Meteorological Society.
Naval Meteorology and Oceanography Command. “Atmospheric Moisture.” United States Navy.

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