The North Island has had one of its driest summers in years, with farmers now feeling the brunt of the lack of water.

Hot, dry weather has many Bay of Plenty dairy farmers struggling to make ends meet as Tauranga stares down the barrel of the third driest month in living memory.

Temperatures on the east coast of New Zealand could reach 40 degrees today and tomorrow, according to a climate scientist, and authorities are on drought watch.

New Zealand is set for a humid summer, with experts predicting a warm and wet January and February.

David Carter has declared a drought in the Waikato and Ruapehu District, saying recent rainfalls appear to have had little effect on dry pastures.

An official drought already declared for Northland could spread to much of the upper North Island.

The drought that has crippled New South Wales for nearly a decade is over.