THUNDER BAY — Last year was the warmest year ever recorded at Thunder Bay Airport, and the second-warmest year in the city since record-keeping began in 1871.
Environment Canada reports that in 2024 the average temperature at the airport last year was 5.4 C, way above the city's long-term annual average of 2.6 C.
Government records show the only warmer year was 1931, when there was a particularly scorching summer that brought the average temperature to 5.8 C.
However, the monitoring equipment in that era was not at the airport but rather on the other side of the city, and its accuracy has been questioned.
According to local climatologist Graham Saunders, what he learned from the granddaughter of the man who served as weather observer at the time has made him doubt the reliability of data from that period.
"What she told me made me fairly skeptical...temperatures were measured on a rooftop near the Prince Arthur Hotel, and that's not the way it's done," Saunders said in an interview Tuesday.
What's also notable about 2024 was the consistently above-average temperatures month after month, from January right through to December, when the temperature at the airport averaged -6.8 C, or almost three degrees above normal.
Environment Canada said ten months were warmer than normal, while two were about average.
Saunders said the impact of a changing climate in the Thunder Bay region is also showing up on Lake Superior, where the surface water is taking longer to cool with the approach of winter, and longer to become dense enough to sink to the bottom.
"I've been watching for a years years the delay in the autumn overturn of the lake, when the water temperature reaches four degrees."
He said the overturn that starts to happen at that point brings nutrients from below to different levels of the lake.
"Fish love it, and oxygen and so on gets mixed into the lake...It's happening later and later. It used to be in early December, and in more recent years it's at the end of December. Last year it happened on the 10th of January, and it will happen any day now."
Saunders said he's been surprised to see how quickly Lake Superior has warmed in recent years.
According to a recent study published in Environmental Research Letters, winter has shortened by two three weeks or more in the Great Lakes region since 1995.
