Hurricane Sandy strengthened before dawn this morning and remains on course to hit Canada tonight with howling winds and drenching rain after blowing through the U.S. eastern seaboard.
Hundreds of Air Canada flights have already been affected and the airline is advising travellers to check the status of their flight ahead of time.
The Canadian Hurricane Centre expects the so-called Frankenstorm to punish parts of southern and eastern Ontario and western Quebec with potentially damaging winds up to 100 kilometres per hour.
The Centre said rainfall amounts will vary from 20 millimetres in some areas to well over 50 millimetres in others. And it says that rain could change into snow over central Ontario.
As of 8 a.m. Monday, the storm was centred about 500 kilometres south-southeast of New York City, moving to the north at 32.2 km/h, with hurricane-force winds extending an unusual 280 kilometres from its centre.
The latest forecast says the rain is not expected to reach the southwestern Maritimes until Tuesday morning, but could persist into Wednesday with total amounts exceeding 50 millimetres.
Seven metre waves could lash the Great Lakes, especially southern Lake Huron, and large waves are also expected to pound Nova Scotia's south shore.
It is a massive storm with tropical storm-force winds that extend some 800 kilometres from its centre.
Sandy was blamed for at least 60 deaths as it churned across the Caribbean.
The centre of the storm was positioned to come ashore Monday night in New Jersey, meaning the worst of the surge could be in the northern part of that state and in New York City and on Long Island. The Canadian Hurricane Centre said in its latest update that there is still a possibility the storm would get stronger before moving on shore.
Higher tides brought by a full moon compounded the threat to the metropolitan area of about 20 million people.
U.S. authorities warned that New York could get hit with a surge of seawater that could swamp parts of lower Manhattan, flood subway tunnels and cripple the network of electrical and communications lines that are vital to the nation's financial centre.
Major U.S. financial markets, including the New York Stock Exchange, Nasdaq and CME Group in Chicago, planned a rare shutdown Monday. The United Nations also shut down.
New York shut down all train, bus and subway service Sunday night.