According to Environment Canada, Lower Mainland residents should brace themselves for a "long episode of rain".

Between Friday (October 15) morning and Sunday (October 17) morning, 75 to 150 millimetres may fall in the central and northeast parts of Metro Vancouver, the North Shore, Howe Sound, and the Sunshine Coast up to Earls Cove.

"Two successive frontal systems will cross the south coast between Friday and Sunday, with high water content associated with an atmospheric river flowing off the Pacific Ocean," Environment Canada states in its weather warning.

"As freezing levels rise to over 2500 metres on Saturday, snow melt will also add to the runoff. Swelling of local streams and localised flooding are likely during this time."

Motorists are advised to be aware that flash floods and water pooling can occur on roads.

The current weather system been dubbed an "atmospheric river", which describes a narrow corridor of concentrated moisture in the atmosphere.

According to a 2015 book called Storm Warning: Water and Climate Security in a Changing World atmospheric rivers can be thousands of kilometres long and 400 to 500 kilometres across.

The author, Alberta-based water expert Robert Williams Sandford, noted that "the warmer the air, the more water these atmospheric rivers can carry", suggesting there's a link between these extreme weather events and climate change.