Agencies across the West Coast are trying to get ahead of the extreme weather setting in

Red Heavy Rain Warnings are in effect for Buller and Westland -- with Buller in a state of emergency.

Latest modelling indicates an easing in rainfall intensity around Westport, but residents in low-lying areas are still urged to consider evacuating.

For the Buller River, the flow range forecast has reduced to about 4000 cubic metres - down from yesterday.

West Coast Emergency Management's group controller Te Aroha Cook says there may be stormwater ponding, surface flooding and seepage from stop banks.

Further south, rivers are still expected to rise in Westland - with rain peaking from late this afternoon.