Environment Canada has issued a rainfall warning for Metro Vancouver and the Fraser Valley, with up to 60 millimetres expected by Monday morning.
It says the warning comes as a moisture laden Pacific frontal system moves into the south coast of British Columbia, bringing heavy rain.
The weather agency says this will intensify by Sunday afternoon before easing into showers early Monday.
The warning says localized flooding is possible in low-lying areas, and that heavy downpours may also cause flash floods and water pooling on roads.
The weather office first issued a rainfall warning for Metro Vancouver on Saturday, but expanded the alert Sunday to cover the Fraser Valley, including Chilliwack and Hope.
Metro Vancouver issued a separate advisory warning that the weather would cause high flows for the North Shore’s Capilano and Seymour rivers.
It noted the rivers can change drastically without much notice.
"Metro Vancouver is urging those who enjoy spending time near the rivers, whether it be using nearby trails, fishing or kayaking, to protect their safety by being alert and extremely cautious," the news release said Sunday.