A transport truck jacknifed and flipped on its side on Highway 40, just outside Montreal, in the midst of the year's first major snowstorm. (Graham Hugues/Canadian Press)

Quebec's first major snowfall of the season is partly blamed for the deaths of two teens in a two-car car crash south of Montreal.

Three people were travelling in the same vehicle on Route 235 near Saint-Hyacinthe around 4:45 p.m. Police said the 17-year-old driver had been trying to pass another vehicle when he struck oncoming traffic.

Two passengers, 16 and 19 years old, died at the scene. The driver was taken to hospital in critical condition.

"The road was icy at this place and the driver didn't adapt his driving to the weather," said Christine Coulombe, a spokesperson for Quebec provincial police.

The driver of the other vehicle suffered minor injuries.

Visibility was fair to poor on most Quebec highways, and dozens of accidents were reported across the province.

Montrealers expecting just four centimetres of accumulation starting Monday morning were instead handed a major snow dump of 25 to 35 centimetres.

Weather office admits error

Environment Canada meteorologist René Héroux admitted the department's computers didn't do a very good job figuring out how bad the storm would be.

"When you forecast two to four centimetres and you end up with 25, there's something wrong going on," he said. "Blame us. I mean, we're the ones who are issuing the forecast, so obviously we are the ones who didn't see it coming."

"In a way, it was a very unusual weather system. They had rain in eastern Quebec — Gaspé, Rimouski and so on — and snow in the west. Usually, it's the other way around," said Héroux.

In Montreal, a small army of snow-clearing trucks was dispatched to start the task of clearing streets.

More than 1,000 snow-clearing vehicles worked overnight on the main roads through Montreal, but by morning, many secondary streets and sidewalks were still knee-deep in snow.

The city's snow-clearing office says it will take five to six days to remove all the snow.

Drivers should heed the following advice, said snow removal director Yves Girard: "Respect the signs, the restriction signs for parking, for the next five days."

Parking is forbidden on the following streets until all snow is removed:

• Notre-Dame Street East (between Georges V and Papineau Streets).
• Sherbrooke Street East (between 81st Avenue and the A25).
• Crémazie Boulevard (between Pie-IX and Acadie Boulevard).
• Henri-Bourassa Boulevard (between Ray-Lawson and Berri).
• Pie-IX Boulevard (between Henri-Bourassa East and Notre-Dame East).
• Papineau Avenue (between Henri-Bourassa East and Notre-Dame East).

High tides cause flooding

Officials in eastern Quebec are assessing the damages from the storm, which caused flooding and evacuations.

Winds gusted above 80 km/h, generating waves measuring more than four metres.

'We haven't seen a storm like this in over 40 years, I've been told.'— Pierre Thibodeau, Saint-Ulric mayor

About 250 people were forced from their homes in communities along the south shore of the St. Lawrence River, including in Rimouski. The towns of Sainte-Flavie, Sainte-Luce and Saint-Ulric declared states of emergency.

"We haven't seen a storm like this in over 40 years, I've been told," said Pierre Thibodeau, the mayor of Saint-Ulric.

On Tuesday,several sections of Highway 132 from the Lower St. Lawrence to the Gaspé remain closed due to flooding.

On the other side of the St. Lawrence, homes were also flooded, with one building in Sept-Îles evacuated after a section of land washed away, leaving the building sitting on the edge of the river.