How does rain clean the air and change sky colours?

In one line

The rule

Rain removes dust, smoke, and other particles from the air by trapping them as it falls, which cleans the atmosphere and can change how sunlight scatters, affecting sky colours.

Let's understand it simply

Imagine your mother sweeping the floor. All the dust rises and floats in the air. Now, imagine she pours a bucket of water on the floor. The dust sticks to the water and settles down. Rain does the same thing in the sky. When it rains, the water droplets catch dust, smoke, and tiny particles floating in the air. These particles get heavy and fall to the ground with the rain. After a good rain, the air feels fresher and the sky looks brighter because there are fewer things blocking or scattering the sunlight.

How it works

1. The air always has tiny particles (dust, smoke, pollen) floating in it.
2. When rain forms, water droplets grow around these particles (they act like seeds for the droplets).
3. As the rain falls, each drop collects more particles from the air.
4. The rain brings these particles down to the ground, cleaning the air.
5. With fewer particles, sunlight passes through the air more easily and scatters differently, changing the sky's colour.

The story behind it

Scientists have studied how rain cleans the air for many years. The process is called wet deposition (removal of particles by rain). Early in the 20th century, researchers noticed that after rain, air pollution levels dropped. Indian scientists also study this, especially in cities like Delhi, where air pollution is a big problem. The colourful sky after rain has been explained by the science of light scattering, first studied by Lord Rayleigh in the 1800s.

Where you see it in real life

• After a monsoon shower in your village: The air feels cool and fresh, and you can see faraway hills clearly. Rain has removed dust and smoke.
• During Diwali: After firecrackers, the air is smoky. If it rains, the smoke clears quickly.
• On a busy road: Normally, you see a brownish haze. After rain, the sky looks blue and clean.
• Rainbow after rain: Clean air and sunlight together make rainbows more visible.
• Sunset after rain: The sky can look orange, pink, or even purple, because clean air lets sunlight scatter more beautifully.
• In the kitchen: When you sprinkle water to settle dust, it is like rain cleaning the air.

Why it matters

• Health: Cleaner air means fewer breathing problems, especially for children and older people.
• Visibility: Pilots, drivers, and train operators can see better after rain.
• Weather forecasting: Scientists use rain to predict air quality.
• Agriculture: Clean air helps plants grow better.
• Exams: Questions about air pollution, rain, and sky colours often come in science exams.

Worked example

Let's say the air in Delhi has 200 micrograms of dust per cubic metre before rain. After a heavy rain:

Given: Dust = 200 micrograms/m³ before rain
Step 1: Rain falls and collects dust particles
Step 2: Dust is washed down to the ground
Step 3: Measure dust after rain = 50 micrograms/m³
Step 4: Air is now 75% cleaner

Common mistakes

• Thinking rain only cleans the ground: It also cleans the air above us.
• Believing all pollution is gone after rain: Some gases (like carbon dioxide) stay; rain mostly removes particles.
• Assuming sky is always blue after rain: It depends on sunlight and remaining particles—sometimes it's grey or colourful.
• Forgetting about humidity: After rain, air can feel sticky because of leftover moisture.

Remember it

Rain is nature’s broom: it sweeps dust from the air and paints the sky with fresh colours.