Updated: Tue Nov. 03 2009 5:14:16 PM

ctvtoronto.ca

A chain reaction crash on Highway 400 stemming from a snow squall is a stark reminder that winter driving conditions are almost here, says an OPP officer.

"I think it's a message to everybody that winter is very, very close by, it's just around the corner, and in some places has arrived already," Const. Peter Leon told ctvtoronto.ca on Tuesday.

About 10 a.m., a snowsquall developed off nearby Georgian Bay at Honey Harbour, approximately 50 kilometres north of Barrie, quickly turning rain to wet snow over Highway 400 "and creating some very treacherous driving conditions," he said.

One collision occurred, involving four vehicles.

After that, a second vehicle went off the road into the centre median where there's a rock cut, Leon said.

As a result of that second collision, a good Samaritan stopped to help. As that person was crossing the highway, "he was struck and killed by a southbound motor vehicle," he said.

Police expect the highway to remain closed until 4 p.m.

Leon didn't have an exact count on the number of people injured, but other than the fatality, he said no one else appeared to be seriously hurt.

As he was coming in to work Tuesday, Leon said the forecast warned that wet snow could occur.

"When that cold air mixes with the rain coming off Georgian Bay, it can be a recipe for disaster. And that was certainly the case this morning."

Highway 89/400

The driver involved in a semi-tractor trailer accident at Highway 400 and Highway 89 before 3 p.m. has died in hospital.

Police say it appears the driver suffered a medical emergency as he was headed southbound. His vehicle broke through the centre median, crossed all the northbound lanes and ended up stopped on an embankment.

When emergency workers got to the scene, he had no vital signs. Paramedics revived the 63-year-old London man and rushed him to hospital, but he then died.