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.

Post-Thanksgiving travel plans were thrown into trouble as almost 30 inches of snow fell along Lake Erie, closing a stretch of I-90 and stranding motorists.

Lake-effect snow blowing in from the Great Lakes has blanketed parts of Michigan, Ohio, Pennsylvania and New York, stranding hundreds of vehicles on roads and snarling post-Thanksgiving travel plans for millions.