About midnight-ish. Peterborough has dropped 6C in the last few hours. It's currently in the Bancroft area-ish. Don't be surprised if we see some fresh white stuff tomorrow morning.
Over the next week or so there will be a couple clippers that will sweep arctic air in behind, bring progressively colder air. The first one is Thursday. It passes to our north so its snow impact is minimal. The one that will release the Arctic hounds will be a week today. I fully expect daytime highs in the -20s and night time lows in the -30s at some point next week. Expect rapid Great Lake freeze up to occur over the last half of January.