A front is expected to bring "significant weather" as it moves across New Zealand Sunday night and Monday.
Forecasters warn it could blast Auckland's commute tomorrow morning with heavy rain and strong northeasterlies, while bringing "extremely high river flows" to the South Island.
"More heavy rain is predicted for the West Coast and the top of the South Island, including areas that recently experienced flooding," NIWA warns.
"Although overall rain won't be as heavy as last weekend, rivers are likely to respond rapidly to these forecast rainfall accumulations. The heaviest rain should occur tonight and Monday.
"Powerful winds are expected across large swathes of the South Island. Many elevated areas will see wind gusts above 100 km/h, and some may reach near 120 km/h."
A NIWA river flow forecasting model shows "extremely high river flows" as a result of heavy rain over the top of the South Island.
Marlborough's Emergency Operations Centre is keeping an eye on the weather with peak rates of 5 to 10mm/h forecast.
"Our emergency response teams will continue to monitor already compromised areas and we will continue to liaise with MetService and NIWA for the latest weather information," Marlborough Emergency Management Incident Controller Dean Heiford says in a statement.
"We are prepared should a response be required."
MetService also has a warning for Aucklanders - prepare for heavy rain and strong northeasterlies during your Monday morning commute.
"There is also the possibility of thunderstorms for northern and western parts of both islands tomorrow."
