Most major Canadian highways to the Pacific port city of Vancouver have been shut due to floods, falling rocks and the risk of avalanches, local authorities said on Thursday.

"This situation is evolving and very dynamic," said the transport ministry of British Columbia, the province where Vancouver - the country's largest port - is located.

"Drivers are cautioned that other provincial roadways could be closed with little or no notice," it said in a statement. Five of the six highways into Vancouver have been closed, although the main route to Seattle is open.

Access to Vancouver relies largely on a limited highway and railway network that crosses the Rocky Mountains, making it vulnerable to severe weather.

In late 2021, an atmospheric river dumped a month's worth of rain in two days on southern British Columbia, triggering floods and mudslides that killed four people, cut off rail access to Vancouver and caused more than C$500 million ($363.35 million) in damage.

Vancouver is a major outlet for resource exports, including potash, coal, forestry products, pork and beef.