Dargaville received 23mm, its lowest since records began in the Kaipara town in 1943.
She said that compounding the problem was that the region had also experienced higher than normal temperatures for the two months.
Dr Griffiths said the situation in Northland was even worse than the drought of 2010, which was then the worst in 60 years.
"And in the short term there's not much relief on the horizon for Northland," she said.
"The highs that have been prevailing and fending off the rain will continue.
"Rainfall totals for the March- May period as a whole are likely to be in the near-normal range for most regions. However, because of the existing soil moisture deficits across the North Island and in the eastern South Island, soil moisture levels and river flows are expected to take some time to recover in these areas."
Dr Griffiths said the "good news" in the longer term was that "the death grips of the high will dissipate during autumn and more normal [autumn] weather will come".
Northland Rural Support Trust spokeswoman Julie Jonker said the rainfall figures showed that it wasn't an over-reaction to declare a drought.
The big dry was hitting farmers hard and it was import ant they not only looked after each other, but also asked for help if they needed it.
"Farmers need to watch their dry stock, keep an eye on their water supplies and they need to be aware that feed supplies are in short supply so they need to plan now, don't wait," she said.
"They need to get their budgets done as soon as possible whether for the banks or if they want to seek Government financial assistance," Ms Jonker said.