Water intake on C pillar and driver floor mat?

Recently I've noticed that during heavy rain the passenger side C pillar and driver side floor mat get wet. There isn't visible dampness between the sunroof and the C pillar, but i guess I can't rule it out? Ain't good when water gets inside and also considering the winter is coming, I don't want something to break due to ice expansion. I'm not a very car type person, have done only basic maintenance so i haven't got a clue how to diagnose these issues, has anyone encountered either of them?