Here's what causes thunder and lightning - as the UK prepares for epic storms

The Met Office has issued yellow weather warnings across the UK for thunderstorms - but what exactly causes the phenomenon of thunder and lightning? This is how thunder and lightning is created - and what to do if you find yourself caught in a storm. What is a thundercloud? The Met Office explains that “thunderstorms develop when the atmosphere is unstable” and this occurs when “warm air exists underneath much colder air”. As the warm air rises, it cools and condenses to create moisture and subsequently a cloud. If the conditions are right, the cloud will build into a cumulonimbus cloud - the type needed to produce thunder and lightning. Within a cumulonimbus cloud, there are updraughts and downdraughts of air. The updraughts carry moisture and water droplets up so high that they freeze and turn into ice crystals. Once they become too heavy to be supported by the updraughts, they fall as hail. During this process, the ice particles bump against each other and give off positive and negative electrical charges. The lighter positively-charged ice crystals are forced up to the top of the cloud whereas the heavier negative charged ice crystals sink to the bottom. What causes thunder and lightning? The negative charged ice crystals are attracted to the positive charge, as well as to charges in nearby clouds and positive charges on the ground. When this attraction is strong enough, the charges join together and discharge, creating flashes of lightning. “Lightning is a large electrical spark caused by the negative charges moving from one place to another,” the Weather Channel explains. Thunder occurs due to the quick expansion and heating of the air caused by lightning. Thunderstorm warnings in the UK Currently, the Met Office displays a yellow weather warning across the majority of the UK for thunderstorms. The yellow warning states that “some places are likely to see severe thunderstorms” but there is “significant uncertainty in location and timing”. This is what the Met Office says to expect: How to stay safe in a thunderstorm There are many myths and misconceptions around thunderstorms which could lead to people getting hurt, such as the idea that lightning never strikes the same place twice, or that it always strikes the tallest object. “Both are false, as lightning strikes the best conductor on the ground - whether it has been struck before or not,” states the Met Office. There are various steps you can take before, during and after a thunderstorm to keep yourself safe. Before the thunderstorm: During the thunderstorm: After the thunderstorm, avoid downed power lines or broken cables.