A trough is expected to move slowly east over the country during Friday, Saturday and early Sunday, bringing rain to many parts of the country. A Watch is currently in force for northern Westland, Buller, Nelson, Mt Taranaki, Northland, Coromandel Peninsula and the Bay of Plenty, for the possibility of rainfall amounts exceeding warning criteria during this time - indicated as a high risk on the chart. In addition, there is a moderate risk of heavy rain about Auckland, Waikato, Waitomo, Taumarunui, Taupo, Wanganui and Taihape from Saturday to early Sunday as this trough passes.
On Sunday, a ridge of high pressure is expected to move onto the country from the west, followed by another trough, which is forecast to move east over New Zealand during Monday and Tuesday. Another burst of rain is expected with this trough, followed by a cooler southerly change late on Tuesday.
and this Map from weatherzone.co.nz says it all: