Torrential rains lashing the Canadian Atlantic province of Nova Scotia threaten to overwhelm a dam and cause major damage in parts of Halifax, the largest city, officials say.
The province’s emergency office said a dam near the St Croix River system could breach and told local residents to leave immediately.
The alert covers a large part of central Nova Scotia.
“Dam overflow – Evacuation order for the St Croix river system area. Dam at risk of breaching,” the province’s emergency management office said in a message sent to mobile phones.
Further south, authorities in Halifax said there had been significant damage to roads and infrastructure and reported abandoned cars on highways.
“It has been a terrible night for our community,” Halifax mayor Mike Savage wrote on Twitter.
Federal Emergencies Management Minister Bill Blair tweeted that the government was ready to help if needed.
Environment Canada said some parts of the province had received more than 15cm of rain.
The flooding was the latest weather-related calamity to pound Canada this year.
Wildfires across much of the country have already burned a record number of hectares, sending clouds of smoke south into the United States.