Ex-tropical Cyclone Uesi is on track to hit New Zealand late on Saturday and bring heavy rain to the West Coast, Fiordland, Southland and Otago.
MetService meteorologist Andrew James said the cyclone was in the northern Tasman Sea with Australia's Bureau of Meteorology issuing a warning for Lord Howe Island and the east coast of Queensland and New South Wales.
From there it will enter the southern Tasman Sea late on Saturday and bring heavy downpours to the western and southern areas of the South Island hit with heavy rain and flooding eight days ago.
New Zealand's first visit from an ex-tropical cyclone this season will not go where it was needed most – in drought-stricken Auckland and Northland.
James said MetService has issued a severe weather outlook detailing significant heavy rain and severe east and northeast gales for the Southern Alps, West Coast, Otago and Southland for Sunday and Monday.
Further weather warnings and details will be issued tomorrow, he said.
James said the reason for the cyclone hitting the southern part of the South Island was to do with how the system was affected by high pressure around it. It was not unheard of for cyclones to hit the South Island, he said, citing Cyclone Gita which bore down on Marlborough, Nelson and the West Coast in February 2018.
WeatherWatch was advising trampers planning to walk in Fiordland and surrounding National Parks to pay close attention to the forecast from Sunday to next Wednesday - and alter plans if necessary.
While it was too early to lock in rainfall totals, preliminary estimates showed between 100mm to 150mm falling for the lower western side of the South Island – and that could potentially double, the website predicted.
It also pointed to the possibility of remnants of the system lingering and reaching the North Island at the end of next week.
"It may only be in the form of showers but Uesi will churn up currents in the atmosphere dragging down more moisture into the Tasman Sea region," WeatherWatch reported.
"There is some modelling showing showers are more likely in the end of February for the North Island."
James said there was no relief in sight for Auckland and Northland before Tuesday next week, and even then the forecast rain will not be significant.