Heavy rain and humid weather is forecast to continue for the upper South Island and southern and central parts of the North Island.
MetService says a complex trough is being preceded by a strong and very moist northerly flow on Tuesday night and Wednesday.
The heaviest falls of 100 millimetres to 130 millimetres in that time are likely to be about Mt Taranaki, the Tararuas and Tongariro National Park, where rainfall rates could reach 20 to 30 millimetres per hour on Tuesday night.
Lower-lying areas of the central North Island could get 50 to 80 millimetres.
In Buller, Nelson and Marlborough, another 50 to 70 millimetres is likely until midnight on Tuesday night.
Streams and rivers are expected to rise quickly and there are likely to be slips and flooding on some roads.
Gale warning for Wellington, Wairarapa
The remnants of tropical cyclone Zelia could bring severe gales to Wellington and Wairarapa on Tuesday night.
MetService says the cyclone, now a low, is expected to move south-east across the lower South Island overnight.
It may briefly bring gusts to about 120km/h to higher parts of Wellington and Wairarapa, including the Rimutaka Hill Road.