I cannot speak for YYZ specifically but early mornings tend to be very busy at many Canadian airports for US preclearance, with the waits decreasing by mid-morning. Often the waits are reported to be close to an hour on peak days during that period.
Are you referring to next Saturday? That generally is before the start of the holiday rush so won't necessarily be a peak travel day, but may well still be busy.
Are you referring to next Saturday? That generally is before the start of the holiday rush so won't necessarily be a peak travel day, but may well still be busy.