Metservice has issued an orange level warning for heavy rain and severe gales across many South Island areas and some parts of the lower North Island.
Strong winds are expected to roll northwards over the South Island on Saturday, before moving onto the lower half of the North Island on Sunday morning.
Metservice predicts heavy rain to the west including the headwaters of the Otago and Canterbury lakes and rivers, which may cause streams and rivers to rise rapidly and lead to slips and surface flooding.
Severe gales are predicted to the south and east of the South Island, with gusts strong enough to damage trees, powerlines and unsecured structures.
Motorists are warned that driving may be hazardous, especially for high-sided vehicles and motorcycles.
Rain watches are now also in place for Nelson, the Tararua Range and Taranaki, and wind watches have been issued for Marlborough, Wellington and Wairarapa.