After a bit of digging - our coldest match ever (no surprise) was the 2016 MLS cup, where (at Pearson) it was -5.3°C at kickoff (windchill -12°) and -6.0°C at the end of the match.
We'll be breaking that tomorrow if the forecast holds, with -9°C at kickoff (-16°C windchill) dropping to -10°C. Good job it's not supposed to be windy. Yeah, definitely snow pants ...