VICTORIA -- Storm-watching season is in full effect in Tofino and Ucluelet as a forceful Pacific frontal system dumps heavy rains on the West Island.

Environment Canada has issued a rainfall warning for the region from Tofino north to Zeballos and Tahsis. The weather service says the storm front is expected to move south throughout the day, hitting communities south of Tofino.

Highway 4 was closed at Kennedy Hill for much of the day Wednesday due to a washout. By 2:15 p.m. the highway had reopened but drivers were urged to use caution.

Environment Canada says West Island communities can expect as much as 150 millimetres of rain to fall.

"Heavy downpours can cause flash floods and water pooling on roads," the weather service said in its alert for the region Wednesday. "If visibility is reduced while driving, slow down, watch for tail lights ahead and be prepared to stop."

Tofino Mayor Josie Osborne posted on Twitter about the storm Wednesday morning, saying driving conditions on Highway 4 were " like driving up a creek bed under a fully running fire hose."