Why we measure the weather

Krishnan in Chennai tells Amir in Kashmir: It's got chilly here after last night's rain. Amir asks: How cold? How can Krishnan explain? What feels cold to Krishnan may feel pleasant to Amir!

Words like chilly depend on who is speaking. Numbers don't. So we need an agreed way to measure temperature, and the other elements too. Knowing the weather hours or days ahead also lets us plan.

Long before instruments, people read nature's signs:

• birds flying low
• ants carrying their eggs to higher ground (heavy rain coming)
• squirrels gathering nuts
• frogs croaking loudly
• pine cones opening and closing

This knowledge was passed down through generations.

Pine cones are a clever example. They close in damp air to protect their seeds and open in dry air to let them fall, so the seeds spread in good weather. A pine cone is really a natural humidity meter!

Even today, in many parts of India, people use traditional signs, especially to guess when the monsoon will arrive. In the last few centuries, scientists have learnt to measure weather very precisely. The careful study of weather and how it changes is called meteorology, and it is the basis of weather forecasts.