"A frontal system will stall over the South Coast this morning, increasing the intensity of rainfall through to Wednesday," Environment Canada is forecasting.
"An additional 50 to 70 mm of rain is expected by Wednesday morning before a brief reprieve from the heavier rain Wednesday afternoon," said the forecast.
Residents are warned to watch out for flash floods and water pooling on roads.
Heavy snow is also forecast for southern interior mountain passes today and tonight.
"Total snowfall accumulations of 15 to 30 cm can be expected with the highest amounts over the Coquihalla summit and Allison Pass," according to Environment Canada.
Motorists are advised to check driving conditions before setting out.
El Nino predicted
Meanwhile, West Coast residents should be expecting above average temperatures this winter according to CBC Meteorologist Johanna Wagstaffe.
"NOAA still predicting a 58 per cent chance of an El Nino this winter, which typically means warmer winters for the Pacific Northwest," says Wagstaffe.
"While La Ninas do have a correlation with higher snowfall, El Nino doesn't necessarily mean less snow, and it doesn't look like it will be a very strong one either."
Across the rest of Canada colder than average temperatures are forecast for the winter ahead.