Bigger storms, more often: New study projects likely future rainfall impacts on NZ

By Muhammad Fikri Sigid, Hamish Lewis, Luke Harrington
Published on April 2, 2026

In the wake of the recent extreme rainfall affecting New Zealand's upper North Island, familiar scenes have emerged: submerged fields, sediment from swelling rivers accumulating against bridges, and floodwaters encircling homes, compelling residents to evacuate.

As we assess the costs of these events, which have inflicted billions of dollars in damages over recent years, questions inevitably arise about climate change's role. A new study investigates the potential severity of future storms in a warming climate.

This research, which employs various warming scenarios alongside the latest climate projections from the Ministry for the Environment, paints a picture of a future in which extreme rainfall events are anticipated to be both more intense and frequent throughout much of New Zealand.

Why and where future storms get wetter

The increase in global temperatures allows the atmosphere to retain more water vapor, consequently heightening the likelihood of heavy rainfall during storms. This trend is supported by climate model simulations, which indicate that the most severe rainfall events are expected to become more pronounced over the coming decades.

By the latter half of the century, projections suggest that the most intense one-day and three-day rainfall events may increase by approximately 10% to 20% across many regions of New Zealand, contingent upon future emissions scenarios.

Areas such as the central North Island and segments of the South Island's west coast are projected to experience significant enhancements in rainfall intensity, while regions like Hawke's Bay and certain parts of Canterbury may see smaller or more variable alterations.

Under a moderate emissions trajectory, by the end of the century, it is estimated that around half of the analyzed locations could witness at least a 50% rise in impactful rainfall events—events historically occurring approximately once every decade. Nearly 30% of these locations could experience a doubling of such events, while close to 10% might face a tripling.

When history repeats

Historical records of extreme rainfall, such as the May 1923 flooding in North Canterbury and more recent occurrences like Cyclone Gabrielle, illustrate the cyclical nature of severe weather in New Zealand. These storms have transported extensive moisture across the ocean, leading to significant flooding.

While future storms are likely to arise from comparable weather systems, their impacts are projected to be substantially more severe, underscoring the urgent need for New Zealand to enhance its preparedness for flood risks and adapt to an increasingly erratic climate in the coming years.