Severe weather has cut Collingwood in Golden Bay off from the outside world

Nelson Tasman Civil Defence Management says the township has lost all phone, mobile and internet coverage.

The main highway between Collingwood and Takaka has also been damaged by flooding and slips and has closed.

Geotechnical engineers will need to complete a full assessment before a single land of the road reopens to light cars only.

The assessment's expected to take some time - and it's unlikely the highway will reopen today.