A snowmobile seemed to be the most logical form of transportation in Lambton County. Traffic was at a crawl in Petrolia, Ont., with blowing snow making driving next to impossible. (Heather Wright/CBC)

A state of emergency has been declared near Sarnia, Ont., where police and Emergency Medical Service workers are trying to rescue about 300 motorists stranded on a southwestern Ontario highway because of extreme winter weather conditions.

Lambton County Warden Steve Arnold declared the state of emergency as of 9:45 p.m. ET on Monday, Western Region OPP said in a news release.

Emergency Management Ontario also issued what it called a "red alert" for the area from Sarnia to London because heavy snowfall was causing zero visibility.

Police said they are co-ordinating efforts to get out onto Highway 402 to rescue people while a snow squall warning was still in effect for the area with a wind chill making it feel like –22 C. More than 360 vehicles needed assistance on Highway 402 between the London Line overpass and Sarnia, they said.

"Police rescuers are experiencing extreme weather challenges in reaching stranded motorists. However [they] remain vigilant in their resolve to get stranded motorists to safety," the OPP said in the release.

Motorists were advised to tune into local radio station CHOK AM1070, FM 106.3 or FM 99.9 to get the latest rescue updates.

They were told to stay in their cars and to try to pool vehicle resources until rescuers reach them. They were also encouraged to make sure their car exhaust was clear of snow so fresh air would be supplied to the inside of their vehicles.

"Everything possible continues to be done to rescue those stranded by the storm," police said.

Unable to assist calls

Earlier, EMS workers in Sarnia said they were unable to get to some calls in Lambton County because of the weather. Plows couldn't clear the roads because high winds reduced visibility. Many roads were impassable.

There were three calls for service earlier on Monday, where rather than respond in person, paramedics worked with local physicians to instruct patients over the telephone.

Paramedic crews were still on duty Monday night and were responding to emergencies within safe travel zones. Officials expect on-duty paramedics will ride out the storm since replacement crews have been unable to get to work.

Police urge residents to stay home

Sarnia police have been urging drivers to stay off the roads because of snowy, icy conditions.

Police said stranded vehicles are blocking roadways, holding up road-clearing efforts in rural areas and preventing police from helping troubled motorists.

Police reported that roads running east from the Modeland Road area were closed Monday afternoon because of dangerous driving conditions. Abandoned vehicles blocking roads would be towed away, Sarnia police said.

Anyone whose vehicle is towed can call Preferred Towing at (519) 344-7277.

"While it may be inconvenient, the road closures have been ordered in the interest of public safety," said Const. Bill Baines in a written statement on Monday afternoon.

Highway 402 closed

The OPP closed Highway 402 from Kerwood Road to the U.S.-Canada border just before noon, saying the road was too dangerous to travel.

West of Guelph, Ont., police responded to a record 543 collisions in 24 hours caused by whiteouts or icy roads, and had to use four-wheel drive vehicles and snowmobiles to rescue stranded motorists.

Any injuries were minor, said OPP Sgt. David Rektor.

"There's no magic to this," said a frustrated Rektor, reiterating that people need to think about slowing down in wintry conditions.

The OPP were taking drivers to warming centres at the Lambton Shores Arena in Forest and the Warwick fire hall in Watford.

Lambton College shut its doors and postponed exams Monday, and Lambton County snowplows and Hydro One crews were also idle because of the weather.