Flooding has closed State Highway One south of MIlton in Otago to all but four-wheel drive vehicles and trucks.
Police say anyone travelling on the road needs to drive to the conditions.
Police said in a statement shortly after 9.30pm the road is being constantly assessed and updates will be provided should the situation change.
The road is closed south of Milton which is about 50 kilometres south of Dunedin.
Earlier a man had to be rescued from his car in floodwaters near Kaitangata as a deluge hit the region.
Poor weather conditions in the worst affected areas are expected to ease overnight.