"Consistent rain has come through, and the same weather system that affected Auckland will gradually make its way across the island."
In Nelson, Marlborough and Taranaki a period of intense precipitation lasting up to 15 hours was likely to dump between 100mm and 180mm of rainfall.
Ms Flynn said Rotorua and western Bay of Plenty were in for an expected 50mm to 80mm of rain tonight.
A severe thunderstorm warning was issued for Wellington and surrounding areas today, with the storms expected to be accompanied by very heavy rain and damaging wind gusts.
Weatherwatch head analyst Philip Duncan said the conditions were an anomaly during El Nino.
"The hottest, driest, weather is typically over the next eight weeks. However El Nino seems to be spluttering a bit over the North Island. It feels more like La Nina."
Mr Duncan said the wet weather would be welcome in areas that had been affected by arid conditions, especially farmers.
"The drought in Canterbury remains in force, but even Canterbury has seen some rain this month, and more coming overnight and tomorrow [Tuesday]."
"This wet weather will also bring moisture into other dry regions such as Otago, Wairarapa and other lower and inland North Island areas, these areas all need rain."
Forecast
Whangarei: Mainly fine, chance shower. Northwest breezes. High 27 Low 16
Auckland: Early rain, then mainly fine, chance shower. H 26 L 17
Tauranga: Morning rain, chance heavy, then odd shower. Northerly. H 24 L 17
Wellington: Rain easing to few showers morning. Northerly strengthens. H 22 L 16Source:
