What's the meaning of " Tell-tale signs" and " spell trouble" ?
I just read a sentence here

" As he makes his way back and forth between the sea and the beach , his eyes carefully scour the skies for any tell-tale signs of rain-even a few drops can spell trouble" ... I can't get it... tell-tale is a specific term to describe sign of rain?? How can I use tell-tale and spell trouble in the daily conversation?

Question

What's the meaning of " Tell-tale signs" and " spell trouble" ?
I just read a sentence here

" As he makes his way back and forth between the sea and the beach , his eyes carefully scour the skies for any tell-tale signs of rain-even a few drops can spell trouble" ... I can't get it... tell-tale is a specific term to describe sign of rain?? How can I use tell-tale and spell trouble in the daily conversation?

Answer

A tell-tale sign is a sign that tells you something with strong certainty. For example, if an old man has yellow hair instead of white, it is a tell-tale sign that he is a strong smoker. 
To spell trouble means "to predict trouble" or "to call for trouble". A drop of rain can predict a thunderstorm. Annoying a strong bully can spell trouble - a fight?