What is the weather?
It's a beautiful day. The sun is shining. It's warm outside. When we say this, we are talking about the weather. The weather is the state of the atmosphere in a specific place at a specific time. It can change from one day to the next, and even from the morning to the afternoon!
The four main elements of the weather
To describe the weather we look at four elements. Each one has its own weather instrument.
How hot or cold it is.
The movement of air in the atmosphere.
The amount of water vapour in the air. We cannot see it, but we can feel it: we sweat more in humid places.
Water that falls from the sky to the Earth's surface: rain, snow, hail and sleet.
Sailors invented a scale from 0 to 12 to describe the wind by what it does. 0 is calm (smoke goes straight up), 2 is a light breeze (you feel it on your face), 8 is a gale (it breaks branches off trees), 10 is a storm (it pulls trees out of the ground) and 12 is hurricane force.
When a rain gauge measures 1 mm of rain, it means that 1 litre of water has fallen on every square metre of ground.