Lake vessels (vessels that do not leave the Great Lakes) ship product from early to late March (weather depending) until well into January early February. Ice conditions will depend on the length of their season.
Ocean vessels arrive through the St. Lawrence Seaway from late March until the end of December. It takes roughly 4-1/2 days to sail from Montreal to Milwaukee. Steel and machinery are typical inbound cargoes and locally grown grain is the main export cargo. Monthly service from Europe to Milwaukee provided by Fednav (fednav.com), and others on inducement.
Inland River Barges can transit to Milwaukee via the Mississippi River, then up the Illinois River along the west coast of Lake Michigan. Manufactured products have arrived from Tennesee domestically to Vietnam internationally. Downbound cargoes include grain and high-wide overweight pieces heading south and overseas.