There are a couple of interesting books about metaphor for people with autism.

It's raining cats and dogs was written by someone with autism: https://www.amazon.co.uk/Its-Raining-Cats-Dogs-Expressions/d...

And here's another book: https://www.amazon.co.uk/Asperger-Dictionary-Everyday-Expres...

Plenty of people process language differently.

That's why there are dictionaries of metaphor to help people understand that "raining cats and dogs" just means "raining heavily".

http://www.amazon.co.uk/Its-Raining-Cats-Dogs-Expressions/dp...

http://www.amazon.co.uk/Asperger-Dictionary-Everyday-Express...

Over-literal interpretation of analogy and metaphor can be a problem.

(http://www.amazon.co.uk/Its-Raining-Cats-Dogs-Expressions/dp...)

(http://www.amazon.co.uk/Asperger-Dictionary-Everyday-Express...)