Why do clouds light and thunder? Where does this cloud lightning come from? We often see lightning and thundering clouds but what is this cloud lightning and where does it come from and why do clouds roar and rumble. Let’s analyze the reason behind cloud lightning and thundering.

Before analyzing cloud lightning and thundering, first let’s understand how clouds are formed and what are their components. Clouds are made of water droplets and ice crystals. When the warm air containing water vapor rises, it cools down. Cool air cannot contain as much water vapor as warm air. Therefore some water vapor condenses onto the dust particles floating in the air which forms a tiny droplet around each dust particle. When large number of these droplets come together, in billions, they form cloud.

The wind inside the cloud carries the less cool water droplets higher into the cloud where temperature is much less due to which these water droplets are converted into ice crystals. Similarly, wind also carries ice crystals from the top of cloud to the bottom of cloud with it. Due to this continuous shuffling and interaction of water droplets and ice crystals an electricity charge develops in the cloud. The top part of cloud becomes positively charged whereas; the bottom part of the cloud becomes negatively charged. Due to this electric potential lightning strikes within the cloud. The electric field with both positive and negative charged particles is always looking to release this charge with the easiest path available. Whenever these negative and positive charges become stronger than the atmospheric pressure inside the cloud, lightning strikes. This is why we see lightning inside or within clouds.

Now let’s analyze the lightning which hits the ground. Why does this lightning hit the ground? When the lower part of the cloud is heavily negatively charged it attracts the positive charged particles from the ground. The positively charged particles on the ground build up due to this attraction around anything that sticks up, like humans, mountains or trees. Whenever the electric potential is strong enough between the cloud and ground the electric field releases its charge. This is how lightning strikes inside, within clouds and, between clouds and ground.
But where do that rumbling, grumbling sound of thunder come from? Let’s analyze the science behind the cloud thunder. When electric field releases its charge it heats up the air around it to tremendous amount. The heated air expands explosively and the surrounding air is compressed. When this heated air cools down it contracts that makes a cracking sound followed by rumbling due to the vibration of air column as lightning strike makes air particles vibrate. The lightning which hits the ground creates a hole in the air called a channel. When it collapses back it makes a sound wave which we hear as thunder.

The speed of light is faster than the speed of sound therefore, we see lightning before hearing thunder. Sometimes the distance is not far so we see the light and hear the sound simultaneously, but when the distance is large we usually see lightning first followed by the thunder.