Rainfall may reach warning amounts over the Bay of Plenty this weekend, Metservice says.
A broad trough and associated front over the Tasman Sea are forecast to gradually cross the country during Friday and Saturday.
This system is preceded by a strong, moist northeast flow and bands of rain and followed by showery northwesterlies.
Heavy falls are expected about western and northern parts of both Islands and a severe weather warning and watch already cover many of these areas.
Video: Sharp Focus Photography