El Niño's 'spiky' temperatures could harm or even kill people this summer, health official warns

Hot weather driven by "spiky" temperatures from El Niño could harm and even kill people this summer if they are not prepared to cope, a senior health official says.

After years of coping with severe flooding, agencies are now turning their minds to heatwaves, drought and wildfire, as what could be the strongest El Niño event on record develops.

Earth Sciences New Zealand (ESNZ) declared El Niño was underway at the beginning of July, and was expected to peak during the southern hemisphere summer.

At a National Emergency Management Agency forum on Thursday, ESNZ and MetService meterologist Jon Tunster said measurements from July were already at record strength for that month, "which is pretty concerning".

"It was worthy of a bit of a fuss earlier in the year, but what's happened now is that we also have observations starting to back it up," he said.

El Niño forms when warmer-than-normal ocean temperatures in the eastern Pacific slow down the trade winds that would normally carry moisture across to Australia, New Zealand and other countries on the western side of the ocean.

For New Zealand, an El Niño generally means wetter conditions in the south-west of the South Island, and drier, windier conditions in most other parts of the country, especially the east and north-east.

Unlike places like Australia and Indonesia, though, El Niño does not necessarily mean a hot summer in New Zealand.

However, ESNZ chief weather scientist Chris Brandolino said temperatures could be "spiky", soaring for a few days before dropping back down.

The organisation had analysed data from the strong El Niño of 1997-98, when very hot temperatures were recorded in Canterbury.

It found that MetService's current heat alert system - which warns of one- and two-day regional temperature spikes - would have been triggered nearly a dozen times that summer for Canterbury residents.

Te Whatu Ora medical officer of health Cheryl Brunton said heatwaves were relatively rare in New Zealand, but even a mild heatwave could have negative effects on people's health.

"Heat is a silent killer and it also harms people relatively silently."

How much harm extreme heat caused depended on the timing, intensity and duration of hot weather, but also how acclimatised a population and its infrastructure and institutions were, Brunton said.

"The evidence suggests that the effects of heatwaves on health are actually greater in temperate areas because extreme heat occurs less frequently and so people simply aren't used to it."

Recent heatwaves in Europe had already caused an estimated 10,000 excess deaths in June, she said.

Health effects could include heat rash, heat exhaustion and heat stroke, and could increase the risk of death for people with cardiovascular, respiratory and other chronic diseases because of the strain on their body's systems.

Anyone who might struggle to cool themselves was at risk - including babies, people who were bed-bound, and those struggling with living costs, Brunton said.

"Lower socioeconomic groups ... might not be able to afford the things that would enable them to adapt, think for example air conditioning."

Renters might not be able to adapt as easily, along with those living in new builds "where it's very difficult to actually open a window even to allow air through".

Brunton raised particular concerns about homeless people, who were currently struggling with freezing temperatures in some places.

"The homeless are going to find it difficult in very hot temperatures as well, because they tend to be within urban areas and that urban heat island-type effect, which can increase those temperatures in that area, is also going to be relevant to them."

Agencies monitoring wildfire, drought conditions

Representatives from Fire and Emergency and the Ministry for Primary Industries told the forum they were closely monitoring soil moisture levels.

MPI national response manager Andrew Curtis said there were already "a couple of spots" around the country that were experiencing a winter drought.

"Parts of the North Island are already starting to go quite dry - they're not getting the precipitation that they would be expecting this time of the year," he said.

"Going into summer, if they start in a hard place, what are they going to look like in mid-January?"

El Niño's typical combination of drying, westerly winds and a lack of rainfall could combine to flip regions into drought "quite quickly", Curtis said.

The good news was that there was still plenty of time for rural communities to prepare, he said.

"We have about six months to do what we can do on-farm, on-property in order to get ready for this."

Farmers should develop a plan now, he said.

That included checking and carrying out maintenance on water supplies and infrastructure, creating livestock and cropping plans for dry conditions, working out where supplementary feed supplies might come from, and how to manage risks to human and animal health from hot or dry weather.

El Niño's effects could be made worse by increased import costs and supply chain difficulties, he said.

"There are commodities, things like [fertiliser], where things may become scarce," he said.

"Things that were available may not be available and that's part of planning - making sure that if you don't get what normally [you can get], where can you get it from? What would that look like for you carrying on through summer?"

Fire and Emergency wildfire manager Tim Mitchell said fire conditions were normal for this time of year at the moment.

Based on previous experience though, the fire season could start as early as September and run longer than usual, he said.

During 1997-98, heightened fire risk had persisted on the eastern side of the country into early April.

The strong winds associated with El Niño contibuted to both drying out wildfire fuel, and driving fires when they sparked, he said.

They could also hamper fire crews' ability to get wildfires under control.

"That [wind] may pose some real operational challenges to particularly our aerial tactics that we may deploy for fires over the season."

New Zealand typically experiences 4,300 wildfires a year. While most were small, 98 percent were caused by human activity, Mitchell said.

Not all areas would experience heightened fire risk, but FENZ was developing a national campaign to raise awareness and encourage people to comply with fire bans and other regulations.

"There is going to be a challenge, I think, around maintaining that public attention, noting just how long the wildfire season may go this year."