Thunder Bay, Ont. residents likely woke up Sunday morning to find a layer of frost covering roofs, decks, and grass, and a local climatologist says that first appearance is the latest on record.

The first frost of 2016 was technically recorded late on Saturday, Oct. 8, said Graham Saunders, which "smashed" the previous first appearance of Sept. 29, 2009.

"[The frost] should have happened a week or two or three or whatever prior to this, but what happened is that we had an inflow of very cold air from northern Canada and it descended on us," he said.

The temperature went down to almost –5 C at the Thunder Bay International Airport that night, Saunders said.

The city also broke another related record this year: Saturday ended 140 straight days without frost, breaking the old mark of 127 consecutive days set back in 2005, Saunders said.

Average frost-free spans last century were less, with around 99 days, he added.

With the warm temperatures we've seen this fall, Saunders said it wasn't the fact that records were broken that was a huge surprise, but by how much they were.

"Usually, when [weather] records are set, you beat the old record by a day or two or three, but this is a matter of weeks."