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What causes weather?

The seafront at Dunoon, Scotland, on a windy dayWeather is a word to describe what is happening in the air: rain or snow, hot or cold, cloudy or clear, windy or still. The Sun’s heat is vital to our weather. It makes some lands warmer than others. The land warms the air above it. Warm air rises, so cooler air flows in to replace it, producing winds. 



The same scene in different weather conditions (clockwise from top left): fog, sunshine, rain and snow
A magnified view of the ice crystals and water droplets that make up clouds

Clouds and rain

Clouds consist of millions of tiny water droplets or ice particles. When water vapour in the air condenses, water droplets form around dust particles. If the temperature falls below freezing, the droplets turn to ice. They float in the air until they become too heavy. They then fall (precipitate) as rain, or snow if the air below is freezing.

Mawsynram in India is the wettest place on Earth. Over 11 metres (36 ft) of rain falls there every year.

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