I have carpet and padding on my floor and we have lots of rain in the Winter and it is hot in the Summer. We just went from pouring rain 3 days ago to over 100 yesterday and I have never had any moisture or anything in mine. I keep it parked in the garage but take no special precautions and the carpet has been in since 1997 and still looks good. A little faded from being out in the sun and driving but no dampness or mold.
Ron
