Fire danger running high in upper north amid oddball La Nina

The summer fire season has already seen several big blazes - including a large wildfire near Waipori Falls in Otago last month. Photo / Peter McIntosh

Wildfire risk across the upper north and East Coast is running high, despite the presence of a La Nina climate system that usually dampens down the danger.

A national outlook just issued by Scion and Fire and Emergency NZ also found there was high to very high risk of wildfire across Marlborough, Canterbury and Otago.

That danger could worsen over coming weeks - although the unusual La Nina, which has been behaving out of step with its traditional patterns, made the danger tricky to predict.

Under classic La Nina conditions, the north and east of New Zealand would be much wetter right now, given the climate driver's tradition of bringing northeasterly storms and rain to those places, and dryness to the south and southwest.

Instead, northern areas were currently abnormally dry - while fire risk in the south and southwest was low to moderate.

"As we head into typically warmer and drier times of the year, vegetation and soil moisture levels over the coming months will be affected by forecasted warm weather and low rainfall," the outlook said of conditions in the north.

"Consequently, this will elevate the fire risk and contribute to deeper burning and faster-moving fires."

In typical La Nina seasons, fire dangers and severity tended to peak around January or February for the North Island.

This map shows northern areas that have or may develop an elevated risk of high fire danger over the next three months. Image / Scion, Fire and Emergency NZ

Northern and eastern regions - including Northland, Auckland, Waikato, Gisborne, Hawke's Bay and Wairarapa - were expected to see warmer air temperatures, less rainfall and drier soils.

But if January continued to bring big rainfall events as December did, potential for wildfire outbreaks could be pushed down to the low danger levels present across much of the rest of the North Island.

In the South Island, potential danger spots to watch were Nelson, Marlborough, Canterbury, Otago, and parts of Southland - notably Tuatapere and Stewart Island.

This map shows southern areas that have or may develop an elevated risk of high fire danger over the next three months. Image / Scion, Fire and Emergency NZ

The La Nina system was partly blamed for setting up conditions for a fire that razed nearly 50 buildings at Lake Ohau Village in October.

The devastating blaze at the idyllic South Island spot came at a time the arriving, moderate-strength La Nina was bringing stronger westerly to northwesterly winds, instead of southwesterly winds usually seen at that time of year.

Today, rural fires cost the economy about $67m each year.

But thanks to climate change, that figure would swell as fire seasons lengthen by an average 70 per cent in a mere 20 years.

Projections suggest that, by 2040, fire risk in many regions - even wetter places like Taranaki, Manawatu and the South Island's West Coast - would shift from one end of the scale to the other.

Wellington could experience a doubling to 30 fire risk days a year - and coastal Otago a tripling to 20 days a year.