Civil Defence has declared a local State of Emergency, stretching along State Highway 6 from Ross to Makarora.
This means the road between Hokitika and Haast – including the Glacier region and townships in between – is now closed.
Travellers have until 6pm tonight to clear the road.
All travellers are instructed to move to the nearest township, park up and remain in place until the Emergency is lifted.
Anyone camping in the region must immediately pack up and move to the nearest township and seek accommodation in a camping ground or motel.
Police will be patrolling the area and directing drivers to the nearest township.
Emergency Management staff and volunteers will be providing assistance as necessary.
The rain expected this afternoon and tonight will likely cause dangerous river conditions and significant flooding.
Slips and floodwaters are likely to make some roads impassable and could isolate communities.
The Grey and Buller Districts to our north are also expecting heavy rain, but not quite to the same extent.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.
If you must travel this afternoon, you must travel north. Civil Defence will monitor the situation and lift the State of Emergency as soon as it is safe.