Cause of thunder

The thunder is actually the sound caused by the air collapsing back after it has been displaced by the electrical discharge of the lightning. Because light travels much faster than sound, we usually see the lightning before the thunder but they are actually almost simultaneous. The longer the time between seeing the flash and hearing the thunder, the further away the storm is (in fact, the time is about 5 seconds per mile, so if you can count 10 seconds between flash and thunder, the storm is two miles away). Lightning is a discharge of static electricity caused by a difference in potential between the top of a cloud and the bottom or between the clouds and the ground. How this difference in potential is caused is somewhat technical, but it is similar to the way that a comb can be electrified by passing it through dry hair or by the way that sometimes one can get a small electric shock (and even a spark) from stroking a cat.

you see the clouds moving on day when it is clear above or at day but you wont be paying attention when the rain starts as you are worried about well during heavy rains there is huge dense clouds roaming around. now as they are roaming and dont have the ability t think and their own force to stop themselves they solely depends on wind blow and as blowing winds are not unidirectional there is a increase chance of clouds striking each other and as these clouds are moist and whaen the strike they get charged positively and groung becomes negative. so you see electricity travelling toward earth and not toward above sky. that cause thunder. now the cause of sound is by far the strike they had and energy they used to produce sound. during heavy rains airplane take flight above clouds and not under them to avoid lightning. or for better saftey they land down at nearby port.

I think it is the sound of the lightning. The lightening heats up the air so much that it makes that thundering noise.