PIEDMONT TRIAD, N.C. -- It's back to school for most students across the Triad Wednesday, but this cold snap can pose a big problem for buses.

Some districts even started on a delay Wednesday morning to make sure they could get their buses up and running.

Guilford County Schools didn't delay Wednesday, but they did have mechanics working all day Tuesday to crank the buses and make sure they would work.

School buses heat up a little differently than cars. They run on diesel fuel and need to get driving for the heat to really kick in. Guilford County School's Transportation Director Jeff Harris says they take about 15 minutes to get warm.

"Unfortunately every time the driver opens the door to let a passenger on, most of the warm air escapes and the process has to start over again," he says.

Harris explains the cold could sometimes make drivers a little late to pick-up. If that's the case, he says keep an eye on your kids and bring them inside to wait so they aren't stuck out in the cold. Bus drivers have even been instructed to wait longer to give students time to come outside.

When it comes to making a decision about closing or delaying school, Harris says school officials will consider the temperature, how long buses have been sitting, and whether or not they've had the opportunity to crank them to see if they're working.

For the latest on school closings and delays, visit www.wfmynews2.com.