More than 4 million people across five states were under winter storm alerts on Sunday as heavy lake-effect snow continued to bury the Great Lakes region, prompting emergency declarations and the deployment of National Guard troops to rescue stranded motorists.

The lake-effect snowstorm has disrupted holiday travel across the region. Some areas could get up to six feet of snow by Tuesday.

Heavy lake-effect snow hit the region over Thanksgiving weekend, with up to 20 inches of snow still to come early this week.