Since I live in the south, we don't get much snow, but we do get rain. I have had the Monster Mats since 10,000 miles, so hopefully that will keep the majority of the moisture issues to a minimum.
If you have a blocked AC, battery, or pollen filter drain, I think the water doesn't come from the top, but seeps in some other mysterious place. My transmission wiring died by a flood in the passenger side foot well that I never noticed, because the area wasn't noticeably damp. So your monster mats may actually help keep water in that area from your attention.