Outlook Summary
• El Niño conditions persist in the tropical Pacific atmosphere and ocean, strengthening considerably since mid-winter. Impacts on New Zealand’s weather patterns have recently started to be felt and should persist through the outlook period.
• Air flow patterns are expected to favour a prevailing westerly direction, characteristic of El Niño conditions, with a tendency towards southwesterly flows from October. • For more on El Niño 2026, and to view our live El Niño Strength Tracker, visit https://earthsciences.nz/news/el-nino-2026-what-you-need-to-know (live from 2 September)
• Seasonal air temperatures for September – November 2026 are most likely to be near average for the west of the South Island. They are about equally likely to be near average or above average for the west of the North Island and the north and east of the South Island. Above average temperatures are most likely for the east and north of the North Island. Despite the lack of cold signals for the season, occasional cold outbreaks are expected to occur throughout spring.
• Rainfall totals for September – November 2026 are about equally likely to be near normal or below normal for the north and east of the South Island, and the west of the North Island. Rainfall is most likely to be below normal for the north and east of the North Island. Meanwhile, rainfall is very likely to be above normal for the west of the South Island.
• Heavy rain events associated with low pressure systems from the north are expected to be relatively less frequent during the outlook period, and potentially beyond. Instead, the highest risk of notable weather systems will originate from the Tasman Sea or Southern Ocean, with heavy rain events more likely for the south and west of the country. • Below normal rainfall for various regions through winter has led to reduced groundwater recharge. During spring, many of these regions are likely to experience reduced rainfall, more frequent dry spells, and enhanced drying of soils and vegetation, creating challenges for water-reliant sectors.
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• During September – November 2026, soil moisture levels and river flows are expected to be near normal or below normal for the east and north of both islands, the west of the North Island, and the north of the South Island. In the west of the South Island, they are expected to be near normal or above normal.
• Warmer-than-average subsurface ocean temperature anomalies have continued to strengthen and expand across the tropical Pacific, providing clear support for El Niño to intensify further and reach the very strong category early in September.
• Peak El Niño conditions are most likely to occur either in late spring or early summer, with the potential for this event to have significant impacts. It is likely to peak as one of the strongest in recent history, as anticipated over the last few months (see El Niño declared, expected to intensify into one of the strongest on record). The event is already comparable to 1997 and has shown the strongest warming trend on record.
• El Niño is expected to influence spring weather patterns, favouring periods of active westerlies, unusually windy conditions, and greater temperature variability. While these are typical spring features, they are expected to be more pronounced in 2026. The extent and persistence of these conditions will depend on nearby high pressure systems, with the greatest risk of nationwide unsettled weather currently expected during mid-to-late spring.
• Other climate drivers and intraseasonal oscillations, for example, the Indian Ocean Dipole, the Southern Annular Mode and the Madden Julian Oscillation will still contribute to New Zealand’s weather patterns, although ElNiño is expected to be most dominant. In general, these other drivers are moving into phases which support ElNiño-like impacts.
• Sudden Stratospheric Warmings (SSW) are historically rare in the Southern Hemisphere, but in recent years have become more common. Predictability is limited, but there is justification for enhanced monitoring until the risk reduces in October. If an SSW does occur, its impacts on New Zealand’s weather patterns can be delayed by a month or more. The SSW in 2025 occurred at intervals through September, and had impacts through December.
• Out-of-season Southwest Pacific tropical cyclones (July–October) are extremely rare. When they do occur, it is almost always under El Niño conditions. This remote risk does not currently factor into New Zealand’s current Seasonal Climate Outlook, although active monitoring remains in place. The tropical cyclone season formally begins during the outlook period (1 November).
Regional predictions for September – November 2026
The tables below show the probabilities (or percent chances) for each of three categories: above average, near average, and below average. In the absence of any forecast guidance there would be an equal likelihood (33% chance) of the outcome for any of the three categories. Forecast information from local and global guidance models is used to indicate the deviation from equal chance that is expected for the coming three-month period. All outlooks are for the three months averaged as a whole. During these three months, there will inevitably be relatively wet and dry periods, as well as hot and cold periods. The exact range in temperature and rainfall within each of the three categories varies with location and season. However, as a guide, the “near average” or middle category for the temperature predictions includes deviations up to ±0.5°C relative to the long-term mean, whereas for rainfall the “near normal” category lies between 80 percent and 120 percent of the long-term (1991-2020) mean.
Northland, Auckland, Waikato, Bay of Plenty
Probabilities are assigned in three categories: above average, near average, and below average.
• Temperatures are most likely to be above average (50% chance).
• Rainfall totals are most likely to be below normal (50% chance).
• Soil moisture levels and river flows are about equally likely to be below normal (45% chance) or near normal (40% chance).
Central North Island, Taranaki, Whanganui, Manawatu, Wellington
Probabilities are assigned in three categories: above average, near average, and below average.
• Temperatures are about equally likely to be near average (40% chance) or above average (45% chance).
• Rainfall totals are about equally likely to be below normal (40% chance) or near normal (35% chance).
• Soil moisture levels and river flows are about equally likely to be below normal (45% chance) or near normal (40% chance).
Gisborne, Hawke’s Bay, Wairarapa
Probabilities are assigned in three categories: above average, near average, and below average.
• Temperatures are most likely to be above average (50% chance), including the potential for notable short duration warm spells, accompanied by high winds.
• Rainfall totals are most likely to be below normal (50% chance) for the outlook period as a whole.
• Soil moisture levels and river flows are about equally likely to be below normal (45% chance) or near normal (40% chance).
Tasman, Nelson, Marlborough, Buller
Probabilities are assigned in three categories: above average, near average, and below average.
• Temperatures are equally likely to be near average (40% chance) or above average (40% chance). Spring temperatures are expected to be more variable than usual, with large swings between warm and cold, and spells of unusually windy weather.
• Rainfall totals are about equally likely to be below normal (45% chance) or near normal (40% chance).
• Soil moisture levels are about equally likely to be near normal (45% chance) or below normal (40% chance).
• River flows are equally likely to be below normal (40% chance) or near normal (40% chance).
West Coast, Southern Alps and foothills, inland Otago, Southland
Probabilities are assigned in three categories: above average, near average, and below average. • Temperatures are most likely to be near average (45% chance).
• Rainfall totals are very likely to be above normal (60% chance). Spring is likely to see more periods of stormy weather, including heavy rain and unusually strong winds. • Soil moisture levels and river flows are most likely to be above normal (50% chance).
Coastal Canterbury and the nearby plains, east Otago
Probabilities are assigned in three categories: above average, near average, and below average.
• Temperatures are about equally likely to be above average (45% chance) or near average (40% chance). Spring temperatures are expected to be even more variable than usual, with large than swings between warm and cold, and spells of unusually windy weather.
• Rainfall totals are about equally likely to be below normal (40% chance) or near normal (35% chance).
• Soil moisture levels and river flows are about equally likely to be below normal (45% chance) or near normal (40% chance).
The full probability breakdown is:
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