Rain is again falling at the top of the South Island, where Tasman, Nelson and part of Marlborough are under orange heavy rain warnings.
The region is copping another battering from the weather after recent heavy rain events brought flooding and widespread disruptions.
The warnings cover Tasman from Motueka west, Tasman east and south of Motueka, the Nelson city district and Marlborough west of Havelock and north of the Wairau River.
Creeks and streams had been rising swiftly and he told RNZ's Midday Report programme this afternoon the rain could set off more slips.
"What's obvious from this morning's rain is surface water has ponded really fast. A lot of the small creeks and streams have come up really quickly as well and are running pretty full and dirty.
"There remains concern over land stability particularly in areas impacted previously and on the roading network out towards Mārahau and Kaiteriteri and areas like that."
Nelson Tasman Civil Defence has opened an emergency operations centre, with support staff from around the country, including Fire and Emergency New Zealand's swift water rescue team.
Residents should travel only if necessary.
"With high tide at 12pm coinciding with the strongest winds, we are asking that people take care on all our roads (especially our coastal routes), and only travel if necessary."
It comes as an "atmospheric funnel" is bringing significant heavy rain and strong winds to much of the country today and into tomorrow.
MetService said the severe weather was caused by a front moving eastwards, and was expected to last into Wednesday morning. It advised people to keep up to date with the latest warnings and watches.
Orange heavy rain warnings are in place for many areas at the top of both main islands, and for western areas of the South Island. Some strong wind watches are also in place for parts of the North Island.
About 2000 homes and businesses across Northland were without power this morning after a night of heavy rain and strong winds, but power had been restored to most properties by the afternoon.
Some locations in the region near Kerikeri and the Bay of Islands recorded more than 90mm of rain as of 10am.
MetService this afternoon issued severe thunderstorm watches - for Auckland, Great Barrier Island and Coromandel Peninsula until midnight, and for Northland until 6pm.
Meanwhile, Air New Zealand is urging travellers to monitor the airlines app for updated information on cancellations or delays.
Air New Zealand's chief operating officer Alex Marren said their "teams are actively monitoring conditions".
"For those travelling today, we recommend keeping an eye on the Air NZ app for the most up-to-date information on their flight," she said.
Weatherwatch's head forecaster Philip Duncan earlier told RNZ an "atmospheric funnel" had stretched right across the South Pacific.
"When you look at the rain map that covers the South Pacific, you see what looks like a funnel that goes from Vanuatu to Fiji to Tonga and it comes straight down in a v shape and points to the top of New Zealand and the top of the South Island.
"It's not necessarily the biggest rain band in the world, but the fact that it is being funnelled into one point or some narrow points means that we are going to get some very heavy rain stuck in some places like the top of the North Island, the top of the South Island and the West Coast."
Duncan said the top of both Islands were the biggest concern because they "don't normally get a month of rainfall in a day".
He said wind was also set to hit, and power cuts were likely in some places.
"It's pretty widespread but - again it's that tunnel shape - most of the worst of that wind is at the top of New Zealand.
"Really the worst of the winds look to be around Auckland, Northland, Coromandel Peninsula, and my hometown of Te Aroha in the eastern Waikato."
The worst of the weather was expected today, he said.
The Waikato Regional Council is warning that forecast heavy rain and severe winds may cause landslips, surface flooding and bring down trees.
Coromandel in the east of the region is under heavy rain warnings and strong wind watches until tomorrow morning, and the rest of Waikato is under a heavy rain watch.
The regional council's flood co-ordinator, Rick Liefting, said landowners should move stock to higher ground, as the amount of rain could exceed land drainage schemes and flood paddocks. He said the persistent rain of recent weeks had left river levels elevated and catchments were saturated throughout the region.
- additional reporting ODT Online
