A severe weather watch is in place for the top of the North Island with a heavy rain system from the north Tasman Sea reaching land this morning.
Northland was being buffeted by gusts of up to 90km/h and rain had started falling as the sub-tropical low moved south towards Auckland.
Meanwhile, falls of up to 200mm are predicted for Fiordland as a significant weather system sits over the bottom of the country.
Wet weather this week is expected to break the drought for some areas of the North Island where farmers have endured one of the driest summers in more than 50 years.
"So far it's started raining in Northland ... and that's the main rainfall we're waiting to spread further south," MetService meteorologist Brooke Lockhart said this morning.
She said there has already been "patchy rain" in the Bay of Plenty and Auckland was likely to see falls later today.
"It will start getting heavier in Northland this morning and then the rainfall will slowly spread further south.
"Auckland's looking to get a bit of rain early this morning and becoming heavier later in the day.
"All of the upper North Island is expected to get some sort of rain throughout the day. Overnight everywhere south of Taranaki [is expected to receive rain]."
Ms Lockhart said forecasters were still working on rainfall predictions for the North Island.
A new severe weather watch will be released later this morning.
"At present, it appears that the Coromandel Peninsula and Bay of Plenty are most likely to experience warning amounts of rain, but eastern areas of Northland and north Auckland may also come close to warning criteria. If necessary, warnings will be issued closer to the event."
