MetService has lifted a heavy rain warning for Northland as conditions ease, but there is still one in place for Hawke's Bay and Gisborne, which has been extended to Wairarapa on Tuesday.
The flood-prone Hikurangi Swamp, north of Whangarei, is one of the hardest-hit areas.
Dairy farmer Evan Sneath still has flood waters covering half the 100 hectares his cows graze and he plans to cull some as he can no longer feed them.
Mr Sneath says the flooding will cost him about $100,000 a hectare in lost production and regrassing.
Dairy co-operative Fonterra has been able to collect most of the milk from its Northland suppliers, but due to road closures still can't get tankers through to a handful of farms on Tuesday.
A spokesperson says its two Northland processing plants have not been affected and it is business as usual in all other parts of New Zealand.
Farmers in parts of the Rotorua and Taupo regions, and in northern Taranaki, are without power after high winds and tree debris damaged power lines and knocked over power poles.
New Zealand Post says strong winds, flooding and road closures have forced the cancellation of rural mail deliveries in parts of Taranaki and the wider Taupo region on Tuesday.