Nana: Do you know two dogs called Lucky and Flo? They were recently awarded medals by the Malaysia government, according to a report I read in the China Post.
Dain: They awarded medals to two dogs? Why?
It's raining cats and dogs.
A great idiom and one that paints a very colorful picture. However... if there is one thing that show up a competent speaker of English as someone who hasn't really fully grasped the language, it's an over-reliance on idioms. In everyday life, we just don't tend to use them, and so coming from a non-native speaker they seem forced and unnatural. Far more appropriate is :
'It's raining heavily.'