2000 BMW 323 sporadic heat and wet passenger side floorboar

Heater problem
2000 BMW 323 4 cyl Two Wheel Drive 83000 miles

Hi there,

I'm wondering if you might be able to tell me what may be causing the floorboard on the front passenger side to get wet (usually after moderate rain). I've also noticed that the heat sometimes works sporadically in spite of the fact that the thermostat has recently been replaced. Could the two things be related?

Thank you.