Food prices rose 2.7% in August compared to July.
Statistics New Zealand says every food group that it measures went up in price last month.
Fruit and vegetable prices went up 9.6%, grocery prices rose 1.9%, and meat, poultry and fish prices rose 2.6%.
It was the largest monthly increase since July 1989, when the rate of GST rose from 10% to 12.5%.
Over the past four months, poor weather pushed up vegetable prices by 36%.
Compared to a year earlier, food prices rose 10.6%, the largest annual increase since May 1990.