Jeff, I live close to you and the amount of snow n rain we get, I'd make sure your on solid ground. If a new home (not just new to you) the soil will not be "virgin", you will have settling. I know this area well and if I were you, I would go down at least 18" (24" preferably).If not virgin soil, you'll have gotten well below the topsoil. I would dig four holes 18"x 18", where your legs will be and fill with 3/4" or larger stone (or item four)tamped every 4". On top use either p/t wood or SOLID concrete blocks at least 4"thick. If your around Pine Island /Goshen in the Black Dirt, I'd go deeper. Wet grass is slippery, be careful when backing under,or as said use mat's or boards. PM me if you wish.