A deep low over the Tasman Sea is approaching the country and will cross the South Island Thursday morning. The main rainband associated with this low sweeps across central New Zealand and much of the South Island overnight, before wrapping around the low and lingering over the lower South Island for a time on Thursday. As the low begins to move away later on Thursday, a cold front crosses central and northern New Zealand bringing another burst of rain.

The largest rainfall accumulations are expected in Nelson, the north and west of Marlborough, Buller, Westland, the Canterbury High Country and also about Mt Taranaki and the Tararua Range overnight Wednesday and into Thursday. Heavy rain is also forecast for parts of South Canterbury and Otago on Thursday. In all these areas, another 80 to 100mm is expected (or more in some places), but rain should ease over the lower North Island and upper South Island Thursday morning, and elsewhere Thursday evening.

People in these areas are advised to watch for rising or already swollen rivers and streams. Surface flooding and slips are possible and driving conditions may be hazardous in heavy rain.