Weather warnings cover most of coastal British Columbia and wind gusts topping 100 km/h are already lashing Haida Gwaii as the leading edge of a powerful storm hits the province.

Wind warnings are posted for Haida Gwaii, north and central coasts, most of Vancouver Island and the southern Gulf Islands, the Sunshine Coast and Metro Vancouver.

Environment Canada's weather office says gusts of up to 120 km/h are possible in northern regions before easing by noon while winds of 70 to 90 km/h are forecast to hit the south coast by midday.

BC Ferries is telling travellers to check its website after numerous afternoon or evening sailings were proactively cancelled on routes between the mainland, Vancouver Island, Gulf Islands and Sunshine Coast.

Rainfall warnings are also in effect for western Vancouver Island and parts of Metro Vancouver where 100millimetres are expected to drench the island and 60millimetres are forecast for Vancouver's North Shore and northeast sector.

Environment Canada says localized flooding is possible in low-lying areas and heavy snow is also forecast for Whistler and the Sea to Sky Highway, with as much as 20centimetres blanketing the corridor before conditions ease late Tuesday.