This is the 216th most frequent Dutch word.
zag
"Zag" means "saw" (past tense of "see").
In this sentence, the word 'zag' is the past tense of the verb 'zien', meaning 'to see'.
Hij zag de vogel in de boom.
He saw the bird in the tree.
Here, 'zag' indicates the act of noticing or observing an occurrence, in this case, rain.
Ik zag dat het begon te regenen.
I saw that it began to rain.
In this interrogative sentence, 'zag' is used within a question to inquire about a past observation.