今晚正在下倾盆大雨。

It's raining cats and dogs tonight.

Source: Tatoeba

Sentence Composition

1 今晚 jīnwǎn tonight
2 正在 zhèngzài to be in the process of (doing sth); to be currently ...-ing
3 下 xià
  1. down
  2. downwards
  3. below
  4. lower
  5. later
  6. next (week etc)
  7. second (of two parts)
  8. to decline
  9. to go down
  10. to arrive at (a decision, conclusion etc)
  11. measure word to show the frequency of an action
4 倾盆大雨 qīngpéndàyǔ (idiom) a downpour; rain bucketing down