Amid a state of emergency, millions of Americans attempting to travel home after Christmas may see their plans delayed as a winter storm moves across the region, creating potentially hazardous road conditions.

Snow is expected to intensify into the night, with officials warning that this could be the heaviest snowfall the region has seen in nearly three years. Gov. Kathy Hochul is urging New Yorkers to stay off the roads if possible, warning that slick conditions combined with heavy traffic could make travel especially dangerous.

Plows were pre-positioned along more than 220 miles of roadway across the five boroughs, and major highways were treated ahead of the snowfall. Despite those preparations, officials say avoiding unnecessary travel is the safest option.

Air travel is also being impacted. Over the past 24 hours, at least 100 flights in the New York City area have been canceled, with more than 100 others delayed as the storm approaches.

Drivers are encouraged to slow down, leave extra space between vehicles and check conditions before heading out.