Temperatures are dropping into the single digits across the country as dangerously cold air sweeps through, with snow striking some areas as well, resulting in school cancellations and accidents.

The cold snap is responsible for an 18-car pileup in western Pennsylvania that killed two people and injured more than 20 others. It happened after nine trucks and nine cars collided on Interstate 80 on Wednesday afternoon, where conditions were very snowy, according to the Associated Press.

Meanwhile, school districts across the country are delaying the start of classes or simply cancelling the whole day. The wind chill in some areas reached below zero in areas such as Alabama and western North Carolina, as well as the Midwest and the Plains. Many areas also experienced up to a foot of snow.

Authorities delayed classes in Georgia by two hours early Thursday with temperatures expected to dip to -2 degrees when wind child is factored in, and officials urged students to wait in warm areas with their parents while waiting for buses.

In Detroit, the temperature reached 8 degrees on Wednesday, causing the city to adjust school scheduled, with nearly 15 area districts and schools cancelling classes today.

Meanwhile, the cold weather raises concerns about the homeless. A number of cities have opened what are known as “warming stations,” which are typically used for residents lacking heat but are also being used to protect the homeless from the dangerous temperatures.

Law enforcement in New Jersey is attempting to move homeless into shelters. In Alabama, blankets were handed out to 15 tent cities in Huntsville, where volunteer workers encouraged the residents to come inside, using a church as a shelter.

The cold temperatures raise the risk of hypothermia or frostbite for those who live outside.