Some people love ’em. Some people hate ’em, but at any given moment there are an estimated 2,000 thunderstorms going on around the world. In this country, they usually end a period of hot, sticky days because the heat causes warm, moist air to rise quickly and form large cumulonimbus clouds – often rising over 20km high.

Inside these whopping thunderclouds, air currents create strong updraughts and water droplets and ice particles rub against each other. As they bang together, it causes a build-up of static electricity, which results in lightning.

Here’s a bit more science. Positive charges or protons form at the top of the cloud and the negative charges or electrons form at the bottom of the cloud. However, as opposites attract, a positive charge then builds up on the ground beneath the cloud. The ground’s electrical charge concentrates around anything that sticks up, such as tall buildings, people, or single trees. The charge coming up from these points eventually connects with a charge reaching down from the clouds and – zap – lightning strikes.

There’s an age-old saying ‘lightning never strikes twice’, but it’s a myth. Lightning can and will strike the same place more than once, as it doesn’t have a memory. The Empire State Building in New York, for example gets struck by lightning about 25 times each year.

And we don’t want to worry you but an estimated 24,000 people are killed by lightning strikes around the world each year while about 240,000 are injured. A US National Park Ranger called Roy Sullivan holds the dubious record of being struck by lightning the most times. The poor chap was caught eight times during his 35-year career.

Dorset’s famous fossil hunter Mary Anning was struck by lightning as a young child. Those around her were killed, but it was said that the event helped turn Mary into a much brighter and more intelligent young woman than she had previously been.

The words thunder and lightning are linked together with good reason, as you rarely get one without the other. Our distant ancestors believed that thunder was the god of thunder – Thor – becoming angry and throwing his hammer, while according to the Native American myths, it was a giant Thunderbird whose wings were so enormous they created peals of thunder when they flapped.

Nowadays we know that thunder is the audible pressure (compression) wave caused by lightning. The deep rumbling and sharp cracks of thunder are produced as the air around the lightning is super heated and rapidly expands. This creates a shock wave which manifests itself as thunder. The closer the lightning is, the louder the clap of thunder will be.

The sounds produced by thunder have been categorised into recognisable terms. Claps are sudden loud sounds lasting 0.2 to 2 seconds. Peals are sounds changing frequency or amplitude. Rolls are irregular sound variances. Rumbles are of long duration but relatively low in frequency.

You can rarely hear thunder from more than about 10 miles away – so if you see lightning and don’t hear anything, you’re too far away.

We’ve all hidden under the bedclothes, counting the time between the flash and the rumble to judge how close lightning is. Each second represents about 300m. Or if you count for five seconds the storm is about a mile away.

Flash facts

• The life span of a thunderstorm can be as short as 45 minutes or as long as 12 hours.

• Nearly 70 per cent of all lightning occurs in the tropical latitude band between 35° north and south latitude.

• Globally, around 90 per cent of lightning occurs over land because solar radiation heats land faster, causing convection (and thunderstorms) to be taller and stronger.

• People who fear the sound of thunder suffer from a phobia called brontophobia and the fear of lightning is called keraunophobia.

• The word ‘bolt’, often used to describe lightning, has no meaning in meteorology and is an inappropriately used term.

• For centuries there have been documented records reporting unusual behaviour (anxiety, restlessness, and irritability) prior to a thunderstorm. It is thought that some animals are reacting to hearing long-wave sound energy from an approaching thunderstorm.

• Thunder is not only heard during thunderstorms. It is uncommon, but not rare, to hear thunder when it is snowing.