I trust you realize that you probably just jinxed yourself by counting on a mild winter. Prepare for blizzards, Pennsylvania and New Jersey! In the past when I had much larger boats (26' & 28' express cruisers and a 30' flybridge) "up north" I always used blue tarps. Most often there were no problems as long as I kept the cover snug so the wind didn't shred it. One winter, however, it turned into a blizzard of blue confetti all over the storage lot. Frequent checks and adjustments are a must. I never had a problem with excessive moisture building up inside. The way the covers were folded at the stern and bow allowed fairly good ventilation. What I did have a problem with was the tarps rubbing against painted surfaces as they flexed in the wind. I was surprised how abrasive they can be. And you have to be careful where the tarp's metal grommets are when the boat is covered; they, too, can tear up a paint job. Don't ask me how I know. You also have to be sure to pad any sharp corners/edges that the tarp rests against. I found that a swimming pool "noodle", slit lengthwise, was great for padding on windshield frames and such.