More mud is forecast for the North Island despite some warmth this week says WeatherWatch.

"Milder than usual airflows off and on this week aren't enough to reverse the muddy conditions underway across a large portion of the North Island," says a WeatherWatch spokexsperson.

"With high pressure shifting east off the North Island it allows another rain band to move in - and next week low pressure dominates the country."

WeatherWatch says New Zealand remains in a neutral and therefore chaotic weather pattern.

"El Niño has not yet formed and may still be a month or two away. El Niño encourages drier conditions across much of NZ due to more high pressure in the very north and windier westerlies elsewhere.

"Western NZ is often cloudier while eastern areas are often clear skied.

"Until El Niño forms we can expect plenty of variety with winds from the north, east, south and west - but likely more dominant from the westerly side."

WeatherWatch says Hawke's Bay looks to get the bulk of the rain over the next two days - but the North Island is generally exposed to more rain thanks to low pressure moving through.

The driest parts of NZ will be Southland and Central Otago.

MetService advises that there is a possibility of thunderstorms on Saturday afternoon in upper North Island, said MetService forecast.

Except for Otago and Southland, night temperatures may go up to 4C in the South Island and 6C to 7C across central New Zealand.

Christchurch is expected to be around 0C, bringing frosts on Saturday. However, rain is expected only on Saturday afternoon with fresh north easterlies hitting the region.

Temperatures are expected to be between 10C and 14C in the upper North Island, dropping below freezing to -2C in some inland parts of the South Island, including Queenstown and Invercargill.

Waka Kotahi has urged people in the upper North Island to drive to the conditions.

'As we head into the second weekend of school holidays, more people are likely to be on the road, so it's important to drive to the conditions,” says an agency spokesperson.

'This means slowing down, increasing following distances, switching headlights on, and watching for flooding and other debris on the road.”

Waka Kotahi also warned that bad weather could see state highways closed at short notice.

'Drivers are encouraged to check the very latest weather conditions before they travel.”

People can keep an eye on road conditions via the Waka Kotahi Journey Planner website.