Toronto school administrators defended their decision to cancel classes on Wednesday, saying an overnight winter storm raised concerns about the safety of students.

"When you are charged with the responsibility for the safety of 250,000 students, a whole lot of adult learners and 40,000 staff, you have got to be careful. Safety is just paramount," Chris Spence, director of education for the Toronto District School Board, told reporters Wednesday afternoon.

"We will get back to learning tomorrow. There will be lots of opportunity for us to do that."

The Toronto District School Board and the Toronto Catholic District School Board cancelled classes on Wednesday as a storm forecast threatened to dump as much as 30 centimetres of snow on the city.

The brunt of the storm ended up missing Toronto, meaning the storm's impact was only about half of what it was expected to be.

It was the first time Toronto's school boards have declared a snow day since 1999, the year former mayor Mel Lastman called in the army to dig out the city.

Spence said he and TCDSB officials decided to cancel classes at 5:30 a.m. to ensure word had time to reach parents before the morning commute.

"You try to make that decision as early as you can so they can make alternative arrangements," said Spence. "You live in the moment, you make a decision and you stick by it. The guiding principle is safety for students and staff."

Spence he is not aware of the cost of the snow day.

He said he understands why some parents may be frustrated by the disruption, but it is better to be safe than sorry.

He said his daughter received a number of jubilant text messages after the snow day was announced.

"Kids love a snow day," he said with a laugh.