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.
""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.
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