Heavy rain is expected in central New Zealand from tomorrow afternoon and most will see rain on Monday.
MetService said a complex low pressure system over the Tasman Sea is likely to hit central New Zealand on Sunday.
Periods of heavy rain are expected in many regions as the low pressure system moves across the country on Monday.
A heavy rain warning has been issued for Nelson west of Motueka from 1pm tomorrow to early Monday. Up to 130mm of rain could fall, with peak rates of 10 to 20mm an hour overnight.
In the North Island, a heavy rain warning is in place for Mount Taranaki with up to 120mm of rain expected overnight.
A heavy rain watch covers northern Buller, the rest of Nelson, northwestern parts of Marlborough from tomorrow afternoon to Monday morning.
Heavy rain could cause streams and rivers to rise rapidly. Surface flooding and slips were possible and driving conditions could be hazardous, MetService warned.
The wet weather could ease a prolonged drought across much of the country.
Water restrictions were introduced in Auckland on 16 May, as water storage dropped to below 45 percent of dam capacity.
Rainfall in the Hawke's Bay was just 26 percent of the average for the area in April, leaving many farmers struggling to feed their stock.
NIWA said the Coromandel Peninsula got 13 percent of its normal rainfall from January to April. Other parts of the North Island, including Whangārei, Auckland, Waikato, Whakatāne and Napier recorded their driest January to April season on record.