Thunder and lightning are natural phenomena that occur during thunderstorms. Thunder is the sound caused by a nearby flash of lightning and can be heard for a distance of only about 10 miles from the lightning strike. Lightning begins as static charges in a rain cloud. Winds inside the cloud are very turbulent. Water droplets in the bottom part of the cloud are caught in the updrafts and lifted to great heights where the much colder atmosphere freezes them. Meanwhile, downdrafts in the cloud push ice and hail down from the top of the cloud. Where the ice going down meets the water coming up, electrons are stripped off, resulting in a cloud with a negatively charged bottom and a positively charged top. When the strength of the charge overpowers the insulating properties of the atmosphere, lightning happens. As the negative charge gets close to the ground, a positive charge, called a streamer, reaches up to meet the negative charge. The channels connect and we see the lightning stroke. Lightning can occur between opposite charges within the thunderstorm cloud (Intra Cloud Lightning) or between opposite charges in the cloud and on the ground (Cloud-To-Ground Lightning).
Thunder is created when lightning passes through the air. The lightning discharge heats the air rapidly and causes it to expand. The temperature of the air in the lightning channel may reach as high as 50,000 degrees Fahrenheit, 5 times hotter than the surface of the sun. Immediately after the flash, the air cools and contracts quickly. This rapid expansion and contraction creates the sound wave that we hear as thunder. In a fraction of a second, lightning heats the air around it to incredible temperatures—as hot as 54,000 °F (30,000 °C). The heated air expands explosively, creating a shockwave as the surrounding air is rapidly compressed and then expands again.
Thunderstorms develop when the atmosphere is unstable. This is when warm air exists underneath much colder air. As warm air rises, it cools and water droplets combine to create larger droplets which freeze to form ice crystals. As a result of circulating air in the clouds, water freezes on the surface of the droplet or crystal. Eventually, the droplets become too heavy to be supported by the updrafts of air and they fall as hail. Thunderstorms are common occurrences on Earth, and it is estimated that a lightning strike hits somewhere on the Earths surface approximately 44 times every second, a total of nearly 1.4 billion lightning strikes every year.
