Wet rear left carpet after rain 2009 Volvo s40

Hey everyone! I’ve recently purchased a 2009 Volvo s40 and have owned it for around a month, I’ve noticed over the last few days after heavy rainfall that a significant amount of water has been accumulating on my rear left footwell but isn’t accumulating in the front. I’ve read that the P1s are notorious for clogged sunroof drains and was wondering what the best course of action would be to fix this issue. Any and all advice is appreciated! Thanks :)