VANCOUVER -- Environment Canada has issued a rainfall warning for the west coast of Vancouver Island as "a moist Pacific frontal system" approaches.

Heavy rain will begin early Friday morning and continue through Friday night, the federal agency said in its warning.

Between 100 and 120 millimetres of rain are expected by Saturday morning, Environment Canada said, warning that heavy downpours could cause flash floods and water pooling on roads.

Rainfall warnings were also issued for parts of the Lower Mainland Thursday, but as of 6:30 p.m., no other regions of Vancouver Island faced warnings.