Water vapor is a gas in the air. Its amount keeps changing — sometimes there’s almost none, and sometimes it makes up to 4% of the air.
Water in the atmosphere can be:
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- Solid (ice crystals)
- Liquid (tiny water droplets)
- Gas (invisible water vapor — the most common form)
Why Water Vapor Is Important?
- Absorbs Heat It soaks up both sunlight and heat from Earth, keeping the planet warm enough for life.
- Affects Evaporation More water vapour = slower evaporation; less water vapour = faster evaporation.
- Carries Energy It stores latent heat, which fuels weather events like storms and rain.
- Influences Rainfall Places with more water vapour are more likely to get rain.
- Impacts Crops Moist air is good for plants. Dry, hot winds (like the Loo) can hurt crops — especially during the rabi season in northwest India.
- Affects Our Skin Dry air can make skin rough and dry. That’s why we use creams in extreme winters or summers.
What is humidity?
- When the sun heats water, it changes into water vapour and rises into the air.
- This invisible water vapour in the air is called humidity.
- So, humidity = the amount of water vapour in the air.
- It tells us how damp or moist the air is at a place.