Warmer Nights Ahead With Upper North Wetter- NIWA's Seasonal Climate Outlook For May To July 2025
Seasonal air temperatures are expected to be above average across all New Zealand regions, says NIWA meteorologist Principal Scientist – Forecasting & Media, Chris Brandolino.
Wetness is favoured for the northern North Island, with dryness a possibility for the western part of the North Island as well as western South Island, according to the latest Seasonal Climate Outlook for May to July 2025, issued by NIWA.
Seasonal air temperatures are expected to be above average across all New Zealand regions, says NIWA meteorologist Principal Scientist – Forecasting & Media, Chris Brandolino.
''Low pressure systems forming north of the country are expected to affect New Zealand and may lead to heightened risks for heavy rainfall events. In the absence of strong large-scale climate drivers, local and regional influences – inherently less predictable – are likely to dominate New Zealand's climate over the forecast period.'
NIWA Outlook: May – July 2025
Outlook Summary:
Neutral El Niño – Southern Oscillation (ENSO) conditions are now present in the tropical Pacific.
The Southern Oscillation Index (SOI), and sea surface temperatures (SSTs) in the central Pacific (in the Niño 3.4 region), which are standard indices for monitoring ENSO, are in the neutral range.
International guidance indicates about an 80% chance for the tropical Pacific to remain in an ENSO-neutral state over the forecast period.
However, intermittent La Niña-like atmospheric patterns may still occur over the next three months.
For New Zealand, higher than normal atmospheric pressure is expected to the east of the country, leading to northeasterly flow anomalies that may shift to a more northerly direction towards the end of the three-month period.
Low pressure systems forming north of the country are expected to affect New Zealand and may lead to heightened risks for heavy rainfall events.
Seasonal air temperatures are expected to be above average across all New Zealand regions, with particularly warm overnight temperatures driving this trend.
May – July rainfall totals are expected to be above normal for the north of the North Island. For the western regions of both the North and South Islands, rainfall is forecast to be near normal or below normal. For the rest of New Zealand, near normal or above normal seasonal rainfall totals are about equally likely. Sub-seasonal, or monthly, projections of rainfall and dryness are updated daily through the NIWA35 forecast.
Ocean waters around New Zealand are currently much warmer than average, with extended offshore areas experiencing Marine Heat Wave (MHW) conditions. Global climate forecasts indicate that SSTs in the New Zealand region are likely to remain overall higher than average for the next three-month period, although the intensity may decrease.
During May – July 2025, near normal soil moisture levels and river flows are expected in the north and east of the North Island. In the north and east of the South Island, near normal or above normal soil moisture and river flows are forecast. In the west of both islands, normal or below normal soil moisture are forecast, while river flows are anticipated to be in the near normal range in the west of the South Island, and below normal in the west of the North Island.
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
RNZ News
16-07-2025
- RNZ News
Concern as signs point to more heavy rain for Nelson Tasman region
The Nelson Tasman region is facing months of work to recover from recent bouts of bad weather. Photo: RNZ/Nathan Mckinnon Forecasters say more bad weather is brewing which could bring significant rain to parts of the country, including the top of the South towards the end of this month and into early August. Earth Sciences New Zealand (formerly GNS Science) meteorologist Chris Brandolino said the next seven to 10 days would be dry from tomorrow. It would bring some short-term respite for those involved in the cleanup in the Nelson Tasman region. However, there would be "a pivot point" as the end of the month approached and more heavy rain could be on the horizon. Brandolino said the source centred on the Tropics which has been experiencing a lot of unusually warm water and there was a tilt toward La Niña conditions. When that happened in the north it resulted in more rain and thunderstorms in Australasia. "So when these lows come across from Australia or the Tasman Sea there is this source of moisture pooling and waiting, and if that area is active with rain and thunderstorms, that low pressure over the Tasman Sea when it does form, it can tap into that moisture over the Coral Sea, over Papua New Guinea, over the West Pacific and the Tropics and siphon that down." That is what the top regions of the South Island have been experiencing in the last few weeks, Brandolino said. "It is a river in the sky that's able to leverage that moisture and turn it into rain." It would take a break but in about 10 days the weather would change again. "That's the concern - there could be these areas of heavy rain again ... those are the themes that are emerging for very late this month and as we work into the first week of August." An example of some of the widespread damage to roads and infrastructure in the Nelson Tasman areas. Photo: Supplied/ Nick Smith An army of volunteers has swung into action in the Nelson Tasman region to help flood-affected farmers and orchardists with the massive cleanup ahead. It comes as the government announces a $600,000 support package for farmers, growers and foresters across the battered district. The chairperson of the Top of the South Rural Support Trust Richard Kempthorne told Morning Report the funding was "great news" and "very helpful". He expected there would be a lot of requests to the Mayoral Relief Fund, which will receive the largest portion, for things that weren't covered by insurance. As a former mayor of Tasman District, he had seen many adverse weather events. "This surpasses all of them by quite a chunk. ... It's just enormous, you cannot plan for it." The cleanup could be "swamping and daunting" and he advised people to try and take it one step at a time to avoid being overwhelmed. Farmers and growers should ask for help if they needed it, Kempthorne said. Silt, stones and debris would need to be removed by heavy machinery while the standing up of fences would also be a priority. There was a lot of thought going into what needed to happen in the river system and stopbanks in the longterm, Kempthorne said.
RNZ News
14-07-2025
- RNZ News
Flash floods - How do they happen and do we get them in New Zealand?
People look on as law enforcement and volunteers continue to search for missing people near Camp Mystic, Texas on 5 July 2025. At least 130 people have died and dozens are missing after the flash floods. Photo: Ronaldo Schemidt / AFP Explainer - Hundreds are dead or missing in Texas flash floods. The Tasman District has been hit hard in recent weeks. What is flash flooding, and why is it so hard to predict? The terrible power of water has been in the news lately, between the Tasman region's massive "100-year floods" and the deadly flash flooding in Texas that has claimed 130 lives and left nearly 200 people missing. There's been a lot of talk about "flash floods" and the carnage they can cause, but how is a flash flood different from more common flooding caused by heavy rain? Here's what you need to know. A flash flood is a flood - just far faster, and often, deadlier than other flooding, which typically comes with just a bit more warning. "The main difference between flash flood and regular flooding is speed on onset of flood," said NIWA hydrologist Shailesh Singh. "As [in] the word flash, flash flood onset very fast can happen within few minutes to few hours as compared to regular flood [that] occurs gradually." Location matters, as being close to a river, creek or in a narrow canyon can create more of a risk. "There are lots of different factors that can lead to flash flooding, including elements such as the topography of an area and how a river is flowing," said MetService meteorologist John Law. In Texas, the devastating flash flood that swept through the hill country along the Guadalupe River on the weekend of 4 July left hundreds of people dead or missing, many of them children. The river rose 26 feet - nearly 8 metres - in mere minutes, stunning residents. Watch: Timelapse video shows Texas river rising Rivers flooding can create staggering death tolls. For instance, the flooding of the Yellow River (Huang-He) in China in 1887 is estimated to have killed between one and two million people. Ngātīmoti resident Shiloh Hobi on 13 July, 2025, after slash came through his property. Photo: RNZ/Samuel Rillstone The recent flooding in the Tasman District was catastrophic and has caused immense damage, but most of it hasn't met the definition of a flash flood. "It was forecasted a few days ahead, which doesn't really fit the sudden nature of a flash flood," said MetService Principal Scientist for Groundwater & Hydrological Modelling Channa Rajanayaka. Of course, isolated incidents of flash flooding could still be seen in Tasman. Shiloh Hobi saw what was once a small creek at the back of his Motueka Valley property explode into a massive flood of water, silt and forestry slash in Friday's rain. "It's so wild when a flood like this comes and so many logs together - it's absolutely unpredictable," he told RNZ. Flash floods are "short but can be really destructive," Rajanayaka said. "Regular floods tend to build up more slowly and they usually give you more warning." In Texas, the Guadalupe River has been prone to flash flooding for many years, a long and narrow river basin where "the steep topography produces rapidly rising river stages during storm periods, leaving residents with little warning time," the US Geological Survey says . There have been multiple fatal floods there in the past, too. There have also been questions about the locations of homes within flood zones and close to the river in Texas, including a camp where dozens of children were staying . The deadly floods also came in the middle of the night, catching many off guard. But there is also a vulnerability in New Zealand, "especially in steep hill country or in cities/towns where water can build up quickly", Rajanayaka said. Historically, several deadly events in Aotearoa have been attributed to flash floods, such as when 21 people were killed in the Kōpuawhara flash flood of 1938 which struck workers at a railway building site. Two people are guided across dangerous floodwaters in Tasman on Friday 11 July, 2025, by members from Fire and Emergency NZ's specialist water response teams from Christchurch and Nelson, using long poles to test what lies under the water. Photo: Supplied/ Fire and Emergency NZ New Zealand is particularly prone to flooding, with 425,000 km of rivers and streams, according to the Ministry for the Environment. "In terms of meteorology, understanding the intensity and location of rainfall is key to forecasting areas likely to be impacted by flooding," Law said. He said Severe Weather Warnings highlight areas that are likely to see heavy rainfall and these are used by hydrologists to model how rivers and streams will respond. "In addition to the broad areas of rainfall covered by Heavy Rain Warnings, some of our heaviest rainfall can be in the form of small scale but intense thunderstorms and downpours of rain," he said. "These can produce extremely large amounts of rainfall in a very short space of time, leading to localised flooding." A sample of NIWA river flow forecasting system video research. Photo: Screenshot / NIWA Pinpointing exactly where downpours will develop is a harder forecast, Law said. "Severe Thunderstorm Watches are issued to highlight areas where all the ingredients come together and there is a potential for intense rainfall. "Once a severe thunderstorm has developed, it is tracked using radar and Severe Thunderstorm Warnings are issued which show the predicted movement of the storm over the next 60 minutes." A variety of local government authority hydrological forecasting systems are in place across the country. NIWA is developing a national river flow forecasting system as well, with a model prototype that has been put forth as a case study . A painted broken heart is seen near Camp Mystic along the Guadalupe River in Hunt, Texas, on 8 July 2025, after severe flash flooding over the July 4 holiday weekend. Photo: RONALDO SCHEMIDT / AFP For flash flood and flood risks in general it's good to be prepared. "We don't have a separate set of advice for flash flooding, as it is essentially flooding that happens rapidly," said National Emergency Management Agency communications manager Anthony Frith. "The general advice stands; pay very close attention to weather watches and warnings, and - super important - evacuate to higher ground immediately if you encounter rising floodwaters. "Don't wait for an official warning for a phone alert. Or as our campaign slogan says - get the flood out ." NEMA's Civil Defence flood preparation website warns people to find out what the flood risk is in their area. "Practice your emergency plan and your evacuation route to higher ground," it recommends. "Take measures to reduce potential flood damage and make sure your insurance policy covers you for flood damage." NIWA's Singh said property owners can mitigate some possible impacts as well. "Maintaining vegetation cover and reducing soil erosion on hill slopes to reduce runoff can be adopted to minimise the risk." Another big risk during flooding is attempting to drive through flood waters. Even a relatively small amount of water can damage cars or strand them. In America, it's been reported by government agencies that over half of all flood-related drownings occur when a vehicle is driven into hazardous flood water. Flooding caused by a flash flood at the Guadalupe River in Kerrville, Texas. Photo: RONALDO SCHEMIDT / AFP Flash floods can move incredibly fast, and even the best planning can be caught off guard. There have been questions about the response in Texas by emergency services, and whether emergency alerts were issued in time . Texas' Republican governor has pushed back at any attempts to cast blame, while Homeland Security Secretary Kristi Noem has denied reports recent policy changes under the Trump administration have slowed disaster aid . In New Zealand, the emergency mobile alert system can be activated during extreme weather. Mobile alerts were issued during the recent flooding in the Nelson region. In the end, the terrible truth about flash floods is that they are inherently difficult to see coming. "It's pretty hard to forecast exactly, because it happens so fast and in such small areas," NIWA's Rajanayaka said. "The scale makes it tough. But better warning systems, smarter land use, and good drainage can definitely help reduce the risk." Sign up for Ngā Pitopito Kōrero , a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
Otago Daily Times
08-07-2025
- Otago Daily Times
More drenchings forecast
A truck and a car negotiate recent flooding in Portobello Rd, near Bays Junction. PHOTO: STEPHEN JAQUIERY More significant rainfall and flooding events may drench coastal parts of Otago over the next three months, as moisture from the tropics and low pressure systems flow over the country. Earth Sciences New Zealand (formerly Niwa) forecasting principal scientist Chris Brandolino said global climate models were strongly signalling the possibility of enhanced low-level convergence in the western Pacific and areas north of New Zealand. "This could draw tropical and subtropical air masses into our region, increasing the likelihood of wetter-than-normal conditions over the next three months. "There is therefore an elevated risk for heavy rainfall events, including those associated with landfalling atmospheric rivers." It could lead to potentially significant rainfall and flooding events, he said. However, it also meant seasonal air temperatures between July and September were expected to be above average across all regions of New Zealand. "Thus, while cold snaps and frost will occur, they are expected to be less frequent than usual." Around coastal Otago, temperatures were most likely to be above average, rainfall totals were about equally likely to be above normal or near normal, and soil moisture levels and river flows were about equally likely to be near normal or above normal, he said. "Chances for heavy rainfall events are considered elevated during the three-month period, potentially leading to flooding, particularly in areas with saturated soils." On the West Coast, Southern Alps and foothills, inland Otago, and Southland, temperatures were also most likely to be above average, he said. But rainfall totals were about equally likely to be near normal or below normal, soil moisture levels were about equally likely to be near normal or above normal, and river flows were most likely to be near normal. Mr Brandolino said Enso-neutral weather conditions remained present in the tropical Pacific. Last month, atmospheric patterns in the Pacific continued to be intermittently consistent with weak La Nina conditions, but more recently, ocean temperatures had shifted away from previous La Nina-like characteristics.
