This satellite image, captured a week ago, shows Lake Superior with nearly 90 per cent ice coverage.
Ice coverage on the Great Lakes will cause a slow start to the shipping season.
More than 90 per cent of Lake Superior is covered in ice, only the second time that's happened in 40 years. With a majority of the shipping system covered, ice breakers will need to cut channels through entire lakes, which Thunder Bay Port Authority CEO Tim Heney said is very unusual.
"Normally you just break out the harbour and the ice flows out into the lake," he said.
With ice being four feet thick in the harbour, about a foot more than average, the port is probably going to need larger ice breakers this year to maintain the channels as ships convoy.
"But how long it takes them to do the job this year and then how many ships move up through that ice will be the question," Heney said.
Those breakers will need to maintain the channels, otherwise wind could close them back up and trap ships.
Ice has already pushed the opening of the Welland Canal to March 28, five days later than last year.
Heney expects the season to be delayed by several weeks. But once up and running, he said Thunder Bay has enough capacity to make up for lost time.
"It really won't have an impact," he said.
But ice at the end of last shipping season meant 200,000 tonnes of grain shipments didn't go through. It also meant that the usual three or four ships that come into Thunder Bay for repair was cut to one.