Temperatures for the top of the country for the rest of the week would reach a maximum of 12C to 14C, "which is pretty cold for up there".
The cold snap would bring overnight lows of 0C in Auckland, 3C in Thames and 1C in Paihia and Russell, Ms van Laanen said.
Northland Civil Defence said they weren't expecting enough heavy rain to cause problems, and were not making any special arrangements for the cold.
"We don't anticipate that those low temperatures will cause us too many issues," spokesman Graeme MacDonald said.
"Those people that have moved out of their homes, they're being well looked after."
Almost all residents who lost power during last week's storms had been reconnected, he said.
Civil Defence had contacted those still without power and most were "happy with arrangements they have in place".
The main priority for the region was to have State Highway 1 repaired after a large slip pulled half the road away.
Contractors were working 24/7 on putting a detour in place, Mr MacDonald said.
Dozens of other roads remained closed today, with many not expecting to be cleared until tomorrow night.
The AA Roadwatch website showed 31 roads either completely or partially closed today.
Meanwhile MPs have toured the flood-hit area, which has been declared a medium-scale adverse event, opening up the way for more government support.
Yesterday the Minister of Civil Defence Nikki Kaye announced a $100,000 contribution to mayoral relief funds being established to provide assistance for community members who were experiencing financial difficulties as a result of the severe weather event.
National MP for Northland Mike Sabin took Ms Kaye, along with Far North District Council councillors and Te Hiku community board members on a tour of affected areas.
The MPs reiterated that the main purpose of their visit was to spread the message that their was assistance available through the Mayoral Fund and to urge people to access it if they needed.
"People need to know that the support is available and we need to get the message out," Ms Kaye said.
Tomorrow's forecast for the main centres:
Whangarei: Fine with southerly winds. High 14C, low 4C.
Auckland: Mainly fine with a few showers and southerly breezes. High 13C, low 0C.
Hamilton: Sunny with southerly winds. High 12C, low -2C.
Tauranga: Sunny with southerly winds. High 14C, low 2C.
Wellington: Showers and southerlies, strong in exposed places. High 9C, low 5C.
Christchurch: Showers, sleety about Banks Peninsula, easing in the evening. High 8C, low 2C.
Dunedin: Morning showers clearing and becoming fine. Southerlies dying out. High 8C, low -2C
