Highlights:

• There is an elevated chance of heavy rain events/flooding during April. Otherwise rainfall totals are equally likely to be normal or above normal across the North Island and near or below normal in the South Island.
• At the start of the outlook period, easterly winds increase the chance of heavy rain, especially from subtropical or tropical weather systems.
• Seasonal air temperatures are expected to remain near average in most regions, with some cold snaps possible later in the outlook period.
• El Niño conditions are looking increasingly likely (about 80% chance later in the year), with a gradual weakening of La Niña influences through this outlook period.

2026 Outlook Summary

• Seasonal air temperatures for April – June 2026 are most likely to be near average for all regions of New Zealand with the exception of the west of the South Island, where near average or above average temperatures are about equally likely. Cold snaps may be more common in the latter part of the outlook period.

• Rainfall totals for April – June 2026 are about equally likely to be near normal or above normal across all regions of the North Island. There is an elevated risk of heavy rain events and flooding, particularly during April. In the west and north of the South Island, rainfall amounts are expected to be near normal or below normal, while near normal totals are favoured in the east of the South Island. Nationally, the risk of drier than normal conditions is expected to increase as the season progresses.

• During April – June 2026, near normal soil moisture levels and river flows are expected for all regions of the North Island as well as the east of the South Island. For the north and west of the South Island, near normal or below normal soil moisture levels and river flows are about equally likely for the next three month period as a whole.

• Easterlyquarter flow anomalies are expected at the beginning of the outlook period, accompanied by an elevated risk of heavy rainfall events linked to sub-tropical or tropical influences. Later in the outlook period, air flow patterns are expected to favour a more

southeasterly direction, then southwesterly air flows, characteristic of El Niño conditions, potentially emerging towards the end of the threemonth period.

• The 2025-2026 Southwest Pacific tropical cyclone (TC) season will officially conclude at the end of April. The Tropical Cyclone Outlook for the season indicates a normal or elevated risk for ex-TC interaction for New Zealand. The risk for tropical cyclone development continues early in upcoming three month period. After a quiet start to the year, the increase in tropical activity over the last month is set to persist through April.

• Neutral El Niño–Southern Oscillation (ENSO) conditions are currently present in the tropical Pacific, although the atmosphere continues to exhibit lingering influences from the weak La Niña conditions experienced during summer.

• Subsurface ocean temperature anomalies in the Pacific are increasingly supportive of the development of a potentially significant El Niño event later this year.

• There is about an 85% chance for ENSO-neutral conditions to remain in the Tropical Pacific over the forecast period (April – June 2026).

• Later in the year, El Niño conditions become increasingly likely, with the probability of emergence rising to around 80% for June - August 2026.

• The next threemonth period is expected to reflect ongoing weakening of La Niña influence, with a gradual shift toward more El Niñolike conditions.

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