Water leaking from passenger side floor vents

Whenever I run the air conditioner or when it rains, my passenger side floor ends up flooded with a 1/4" water.
When there's water in the vents, I can hear it sloshing around when I make turns. When I've had the AC running, it makes a squealing sound when I turn and also hear the slosh. I haven't run the AC in about a month, but it just rained, and once again, I have water in the vents and leaking to the floor board.