rainstorm
涷 centers on a sudden, heavy downpour: a rainstorm. The meaning is specific to a violent, short-lived rain event.
涷 combines the water radical 氵 with 東, which likely contributes the sound. The character is used for a rainstorm, but the exact historical development is uncertain.
Water 氵 pours down from the east 東 in a sudden, violent storm. Picture a typhoon sweeping in from the east, drenching everything.
For トウ, imagine a rainstorm hitting a tall tower: tower -> トウ, and the water 氵 lashes against the eastern 東 side of the tower.