An undeniable wild and extreme force of nature, thunderstorms can be both amazing and deadly all at the same time. The thick, black clouds associated with thunderstorms have the potential to generate the same amount of energy as a small nuclear bomb. That is hundreds and hundreds of megawatts of energy being released in a single thunderstorm. A thunderstorm is defined as a storm that contains both lightning and thunder which is caused by unstable atmospheric conditions. At any given time there are 1800 thunderstorms raging in the world, and annually there are around 16 million thunderstorms.

How are Thunderstorms Formed?

Cumulonimbus clouds are huge, low forming, fluffy clouds. These clouds form when warm, moist air rises and cools, causing water vapour to condense into tiny droplets. During this process of the moist air rising and cooling, heat is given off, which makes the cloud grow larger and the air within it will continue to rise. These gigantic clouds can grow to the top of the troposphere, which is 10 kilometres (6.3 miles) above the Earth’s surface. When clouds reach this point they encounter the very cold air of the stratosphere and cool, which is why storm clouds have a broad, flat top. The top of these large cumulonimbus clouds are made of ice crystals.

Thunderstorms are more common in the tropics because the air in these locations is warmer and heavy with moisture, which are the ideal conditions for creating thunderstorm clouds. Heavy rain, hail, thunder and even lightning accompany these storms. Every day across the globe there are roughly 40,000 thunderstorms.

lightning(127168)Credit: morguefile

Lighting Up the Sky

The ice and water droplets found in thunderstorm clouds create electricity. The top of a cloud develops a positive charge and the bottom part of the cloud creates a negative charge. Lightning strikes when a spark jumps from either one cloud to another or from the bottom of the cloud to ta positive charge on Earth. Lightning causes the air to heat rapidly to 30,000C (54,000F), which makes the air expand, quickly creating thunder.

As the static electricity builds up in the clouds, it will either jump across to another cloud, creating sheet lightning, or hit the ground as fork lightning. Thunder is the noise lightning makes. Lightning causes the air in and around it to heat rapidly, which creates the sound we associate as thunder.

Despite the popular belief, lightning can strike in the same place twice, even hitting the same place multiple times. If there is a thunderstorm and lightning is around, you should take shelter, but do not stand under trees. Lightning is attracted to an area’s tallest object and will often strike trees. Lightning travels at the crazy speed of 37,000 kilometres (23,000 miles) per second and a single bolt can be 6 kilometres (3.2 miles) long. A way to tell if a storm is getting closer is to count the seconds between seeing lightning and hearing thunder. If the time between seeing lightning and hearing thunder is getting shorter, then that means that the storm is moving closer to you.

Hail in Thunderstorms

Hail starts off as frozen water droplets that are caught in a cycle of up and down draughts inside the clouds. As these droplets cycle around the cloud, extra layers of ice are added and build up, causing the droplets to become bigger. Eventually when they become too heavy for the storm cloud and draughts to hold up, they fall to the Earth as hail. The biggest recorded hailstones fell in Bangladesh in 1986 and weighted around 1 kilogram (3.2 pounds) each.  Hailstorms are usually more common in mountainous regions, rather than the areas that have a lower temperature. For a hailstorm to be classified as 'severe', the hailstones must have at least a two centimetre (three-quarter inch) diameter. At that size, the hailstones can to substantial damage to cars and properties.


A recent study has found that there is rich and diverse amount of microbotic life and chemicals within storm clouds. The Danish researchers from Aarhus University published the findings on January 23rd 2013, in the open access journal PLOS ONE. They had analyzed hailstones that had been recovered after a storm in May 2009 and discovered that within the ice there were several species of bacteria typically found on plants and almost 3000 different compounds usually found in soil. 

Thunderstorm Safety

What do you do if you are stuck in a thunderstorm?

Thunderstorms, lightning and hail can be dangerous to people who are caught up in the middle of a storm. On average, around 100 people in the US die annually from thunderstorms and being hit by lightning. Several people also sustain injuries from lightning strikes. These types of injuries and deaths are mainly caused by people being caught outdoors during stormy weather.

If you are stuck outside during a thunderstorm, it is best to avoid open spaces like fields, beaches or lakes, and stay away from tall trees, as they attract lightning. The safest place to be is to go inside your home or car. If you are taking shelter in your car, don't touch anything metal, as it is a conductor of electricity.