A Northland farmer says water up to four-metres deep surrounds most of his property and others, after more rain this weekend in the flood-stricken rural area.
At least 60mm fell, leaving many farmers who were already recovering from last week's storm in worse shape, and under added stress.
Ben Smith is a dairy farmer in the flood-prone Hikurangi Swamp area and said the support from areas such as Bay of Plenty with supplementary feed supplies had been a welcome relief.
But he said some other suppliers were attempting to exploit the dire situation in Northland.
Mr Smith said one supplier that contacted him on Sunday was demanding a 40 percent increase on the price of a load of hay bales.
Civil Defence said up to 60mms of rain fell overnight, north of Whangarei through to Bay of Islands.
The Northland Rural Support Trust says many farmers are in the middle of calving.
Its co-ordinator, Julie Jonker said farmers in the Hikurangi swamp area and beyond are now in serious trouble with some properties 90 percent under water.
This includes areas further west and south, at Kaihu, Mamaranui, Maungakahia and Tangiteroria.
Ms Jonker said the biggest challenge for farmers is ensuring they have enough supplementary feed for their animals.
She said five truck and trailer loads of feed are due to arrive on Tuesday, but even when the land does begin to dry up, farmers will still need on-going feed until at least Spring.