Images from across much of the country illuminate snow-covered streets and preparations for worse still to come.

As millions of Americans hunker down for the winter storm, 17 states and Washington, D.C., have declared states of emergency.

The electric grid in many parts of the U.S. is already under strain due to rising demand from data centers and the slow construction of new power generation.

Forecasters warned the storm’s impacts could linger for days, urging people to prepare for extended cold and power outages.

Experts tell TIME there's a thin line between being prepared and panic buying, and other people have a lot to do with it

On top of heavy snow, forecasters and public officials are worried about slick, icy roads and the potential for sleet and freezing rain to spark power outages.

"Winds will pick up in the afternoon and evening, especially near the coast and could create near white-out conditions/near blizzard conditions with winds gusting 30 to 40 mph at times."

Grid operators deploy emergency measures to keep lights on as extreme weather drives heating demand and strains natural gas delivery systems nationwide.