Parched areas of the North Island could be at risk of surface flooding with heavy downpours and thunderstorms forecast.
It comes after some parts of the North Island experienced their driest summers on record.
Heavy warnings and watches have been in place as an active front makes its way across the country Tuesday and Wednesday.
While the most severe weather in the North Island is forecast tomorrow, Northland and Auckland will see some welcome showers this afternoon and evening thanks to daytime heating and wind convergences.
There is also a moderate risk of thunderstorms in Northland, and low risk in northern parts of Auckland, to the northwest of the city.
MetService meteorologist Angus Hines said today a heavy rain band was sitting over the South Island's West Coast, where a heavy rain warning was in force to 4pm, dropping 100-160mm over the day.
Overnight the frontal system driving the wet weather moves north, eventually affecting the entire North Island, however there will be big variations in rainfall.
Overnight there will be a few hours of rain about the west coast from Wellington to Taranaki.
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As it makes its way northwards over the lower and central parts of the North Island it will bring rain or showers, and a low risk of thunderstorms.
However, for the coast from north Taranaki to Waikato there is a moderate risk of thunderstorms which may be accompanied by heavy rain up to 20mm/h.
By midday the rain band will be over Northland, Auckland and Waikato, again with a few hours of light rain, with most areas receiving under 10mm.
"This system is by no means a drought-breaker, but a slight sigh of relief might be heard across these dry regions," said MetService meteorologist Andrew James.
Auckland Airport recorded just 73.2mm over the three summer months, its driest summer on record since observations began in 1962.
The system will be most active as it shifts east, particularly about the Coromandel, Bay of Plenty, Gisborne and Hawke's Bay.
There is a moderate risk of thunderstorms from early afternoon about Taupō and northern Hawke's Bay, spreading northwards to Gisborne, Bay of Plenty, western Waikato and Coromandel Peninsula during the afternoon and early evening. Some thunderstorms could be severe, with possible downpours up to 40mm/h.
There is also a moderate risk of thunderstorms about southeastern parts of Northland during the late afternoon and early evening, with intensities of up to 20mm/h.
A ridge of high pressure over southern New Zealand extends north over the remainder of the country on Thursday.
The ridge slowly moves east on Friday and Saturday as a trough of low pressure approaches the country from the Tasman Sea, and becomes slow moving to the west of the South Island on Sunday.
This trough is expected to bring rain with heavy falls to the South Island West Coast from late Saturday.
There is low confidence of warning amounts of rain in Westland and Fiordland north of doubtful Sound from late Saturday and also during Sunday.