In a thunder/lightning storm how can you tell how far away it is?

Answer 1

Lightning is an electrical discharge between the Earth and a cloud (in actually fact the initial lightning strike goes FROM the Earth to the cloud, but I won't go into the technicalities now). The lightning strike does two main things as far as the observer is concerned:
1. it creates a flash of light
2. the electrical energy is so powerful that in simple terms it fries the air it's passing through, causing an explosion we hear as thunder.
If you were directly under the point the lightning strikes then you would hear the thunder and see the flash at the same instant.
The difference in time as you are further and further away is due to the different speeds that light and sound travel.
Light travels at 186,000 miles per second (yep thats second - so pretty quick!)
Sound travels at about 760 miles per hour through the atmosphere, which is pretty sluggish in comparison.
The result is that when lightning strikes we see the flash of light almost instantaneously but the sound takes longer to reach us:-
760 miles in 60 minutes
= 76 miles in 6 minutes
= 76 miles in 360 seconds
= 7.6 miles in 36 seconds
= 1 mile in 4.736 seconds

In round figures this means that for every 5 seconds the sound travels a mile.

So if you start counting when you see a lightning flash you can judge how far away the strike was:-
5 seconds = 1 mile
10 seconds = 2 miles
15 seconds = 3 miles etc etc

Incidentally counting the seconds is an excellent way of teaching small children not to be afraid of thunderstorms - they get so involved in counting they forget to be scared!

Answer 2

Count the amount of seconds between when you see lightning and when you hear thunder. Each second equals 1 kilometre. Eg If you see lightning and it takes 5 seconds to hear the thunder, then it is roughly 5km away.

This is a bit of an old wives tale but in my experience it seems to be quite true.

Answer 3

Count between the lightning strikes. The bigger the number the farther away it is.

Answer 4

they say that if you count the seconds between the lighting flash,and the thunder, thats how many miles away it originated.

im not sure if thats entirely accurate, comparing the speed of light and the speed of sound

Answer 5

Count the seconds from the flash to the sound. Sound travels about 1000ft/sec, so if it 5 seconds, the flash is about 5000 feet away.