Lake effect snow is slamming the Great Lakes, with seven states from Wisconsin to New York under snow alerts on Monday.

Lake-effect snow continued to fall on parts of western New York that were already blanketed with a foot or more over the past four days.

Post-Thanksgiving travel will be treacherous in parts of the Great Lakes region on Monday with more lake-effect snow falling after the region was already buried under feet of it, while cold temperatures remain across a large swath of the United States.

In late fall and winter, lake-effect snow is a common occurrence in the Great Lakes region. "Lake-effect snow occurs when cold air, often originating from Canada, moves across the open waters of the Great Lakes.