Ask A Scientist© Environmental Science Archive

Author:      mary b olijr
Why are thunder clouds a dark color?

Response #:  1 of 1
Author:      mortis
Thunder clouds are very thick - they tower up to eight or nine miles from the 
earth's surface.  They appear dark on the bottom because light cannot get 
through from the top all the way down to the bottom, which is the part you see 
when you look up at them.  If you take a sheet of paper and put it against a 
window, you can see light through the paper.  If you put another sheet of 
paper on top you cannot see as much light as before, and if you put a thick 
pad of paper up to the window, you cannot see any light at all - the side you 
see is completely dark.  It is the same with  clouds:  thin ones are light but 
thick ones are dark.