The government has declared a state of drought in Northland and says other regions are likely to follow.
A declaration of drought means farmers have access to a range of relief measures and financial aid.
Primary Industries Minister Nathan Guy says Northland is gripped by an extreme climatic event.
"The entire North Island is extremely dry but Northland is one of the worst-hit areas," he said on Wednesday.
"We are closely watching other parts of the North Island which are extremely dry, in particular the Waikato and Hawke's Bay."
Mr Guy, a dairy farmer, says the North Island is now beyond what is considered a normal dry summer.
The drought declaration applies to the area north of the Auckland Harbour Bridge.
Mr Guy says the decision was made after advice from his ministry which included soil moisture data from NIWA.