You're right of course. The next verse is a big clue. And using a more recent translatin helps:
22 Have you entered the storehouses of the snow, Or have you seen the storehouses of the hail, 23 Which I have reserved for the time of distress, For the day of war and battle?
(NASB)
I'd guess that "treasures" is essentially an archaic form of "treasuries".