6.5 Thunderstorms & Lightning

When moisture and strong winds come together, an ordinary cloud can grow into a towering thunderstorm — crackling with the same static electricity you met when rubbing a balloon in Chapter 5.

How a cloud gets charged

Charge Separation in the Cloud Inside a storm cloud, strong winds rush up and down, and water droplets and ice particles rub against each other — and, just as rubbing charges a balloon, this rubbing builds up static electric charges. The lighter, positively charged ice particles rise to the top of the cloud, while the heavier, negatively charged water droplets sink to the bottom. This charge separation also makes the ground below (and trees and buildings) become positively charged.

The flash and the bang

Normally air is an insulator — it keeps the opposite charges apart. But when the charge build-up grows huge, the air’s insulating ability breaks down, and a sudden flood of charge leaps across.

Lightning and Thunder A sudden flow of charge produces a brilliant flash of light — lightning. It can leap within a cloud, between clouds, or between a cloud and the ground. The lightning superheats the surrounding air, which expands explosively and makes the loud crash we call thunder. A storm with lightning and thunder is a thunderstorm.

A Step Further: India’s Local Storms Local thunderstorms have wonderful regional names. Kalboishakhi (West Bengal, Bihar, Jharkhand) and Bordoisila (Assam) arrive before the monsoon and help kharif crops grow. In Kerala, Karnataka and Tamil Nadu, pre-monsoon storms are called mango showers because they help mangoes ripen, and in Karnataka they aid coffee plants.

Staying safe

Lightning Safety Rules Lightning can start fires, damage buildings and even kill. During lightning:

  • Stay away from tall objects (trees, poles). Find a low, open area and crouch down — do not lie flat.
  • Avoid metal — don’t use an umbrella with a metal rod.
  • Get out of water immediately.
  • Inside a bus or car, you are comparatively safe.

Ever Heard Of… The Lightning Conductor A lightning conductor is a metal rod fixed along a building’s wall during construction. Its pointed top rises above the highest point of the building, and its other end is buried deep in the ground. If lightning strikes, the rod gives the charge an easy path straight to the ground, protecting the building from damage.