With the UK on thunderstorm warning, what causes thunder and lightning?

·2-min read
Several flood alerts remain in place on Monday after rain, thunder, and lightning swept across parts of the UK overnight (Yui Mok/PA Wire)
Several flood alerts remain in place on Monday after rain, thunder, and lightning swept across parts of the UK overnight (Yui Mok/PA Wire)

The Met Office has issued a yellow thunderstorm warning across England, Wales, and Northern Ireland, with some areas to see deluges of 20mm to 30mm of rainfall.

Commuters have been warned to expect disruptions to travel in some places, while motorists have been advised to prepare for more difficult driving conditions affected by hail and spray from water on the roads.

The Met Office also warns there might be some damage to a few buildings and structures from lightning strikes and gusty winds, as well as some short-term loss of power. The wet weather and thunderstorm warning is expected to continue through to next week.

What is a thunderstorm and what causes the phenomenon? Here’s everything we know.

What is a thunderstorm?

A thunderstorm is a short and violent weather disturbance that is associated with lightning and thunder. Though they’re referred to separately, they always occur together.

Lightning is an electrical discharge caused by imbalance within the clouds, or between storm clouds and the ground. Thunder is the sound caused by lightning. Depending on how far you are from the lightning, thunder can be heard as a short, violent crack or a slow, low grumble.

What causes thunder and lightning?

The Met Office explains that thunderstorms “develop when the atmosphere is unstable. This is when warm air exists underneath much colder air”.

They are created by intense heating of the Earth’s surface and are most common in areas of the globe where the weather is hot and humid. In terms of the UK, thunderstorms are commonly found over the East Midlands and the south-east.

Most lightning will be seen between clouds but occasionally they can be seen striking the air or the ground. It is extremely hot; it only takes one strike for the surrounding air to expand and vibrate. This is why we hear thunder a short time after seeing lightning, and also because light travels faster than sound.

Most cloud-to-ground lightning strikes do not touch humans and the odds of them striking someone are very low. However, there is still a very low chance you could be hit by lightning and, in most cases, it can be fatal, as each bolt can contain up to one billion volts of electricity.

There are a few things you can do to avoid being struck by lightning. They include avoiding electronic equipment and water, or standing beneath windows, doors, porches, and concrete structures. Lightning can travel through electronic appliances, trees, and a building’s plumbing.