Forecasters in Halifax say the storm's centre could track anywhere from just east of Cape Breton to well offshore over the Grand Banks.
But they say the system could transition to a strong post-tropical storm when it reaches the Atlantic region late Friday or Saturday, with the strongest winds to the right of the storm and the heaviest rainfall to its left.
Forecasters say it's still too early to predict the storm's track, but suggest it's likely eastern Nova Scotia will be hit with heavy rain.
Parts of eastern Newfoundland could also see storm surges even if the system remains offshore.
The U.S. National Hurricane Center said late Wednesday that Gonzalo had top sustained winds of 195 kilometres per hour and was about 935 kilometres south-southwest of Bermuda moving north at 15 kp/h.
A hurricane warning was in effect for Bermuda, where the government said it would close the island's international airport Thursday night. Several airlines increased the number of flights departing Bermuda ahead of the storm.
— With files from The Associated Press