Q1.
Let us imagine that Krishnan from Chennai is speaking with Amir in Kashmir. Krishnan tells Amir that it has become chilly in Chennai after it rained the previous night. Amir asks him how cold it is. How will Krishnan explain to Amir how cold it is? After all, what is cold for Krishnan may be quite pleasant for Amir!
Answer
Krishnan cannot explain it in words at all — he has to give Amir a number on a scale both of them know. He should say, “It is 20°C here,” instead of “it is chilly”.
Why it happens: ‘Chilly’ is not a measurement, it is a feeling, and the feeling depends on what your body is used to. Chennai is warm and humid almost all year, so 20°C feels cold to Krishnan. Kashmir has real winters with snow, so 20°C is a mild, pleasant day for Amir. The same air gives the two boys two opposite descriptions.
The moment Krishnan says “20°C”, the disagreement disappears. Amir may still think that 20°C is pleasant, but he now knows exactly what Krishnan's weather is like, and he can compare it with his own. This is precisely why the whole chapter is about measuring the weather with common standards — the same is true of rain (millimetres), pressure (millibars), wind (km/h) and humidity (per cent).
Tip: Notice that Krishnan could add one more useful number — the humidity. Air at 20°C that is damp after a night of rain feels much colder on the skin than dry air at 20°C.