Level of annual rainfall

IBISWorld forecasts the annual rainfall level to swell by 0.3% in 2025-26 to 1,628.4 millimetres. Rainfall levels are highly volatile, meaning predicting it with any certainty is very difficult. Consequently, this represents the long-term average rainfall for New Zealand.

According to the latest seasonal outlook from NIWA (Taihoro Nukurangi), normal or above-normal rainfall is expected between September and November 2025 for the North and East of the North Island and the northern end of the South Island. In all other areas, normal to below-normal rainfall is projected.

New Zealand's location heavily influences its climate. According to analysis from the World Bank Group, the country's surrounding ocean, prevailing westerly winds and mountain chains lead to more rainfall in the west and drier conditions in the east. In addition, climate conditions vary between the North and South Islands, with subtropical temperatures often occurring in the country's far north. In contrast, the far south of the country has much cooler temperatures. According to NIWA, more rainfall typically occurs during the winter season in the northern and central parts of the country. Conversely, for the southern parts of New Zealand, the majority of rainfall occurs during the summer season.

Annual rainfall is a highly volatile measurement. For example, the 2020-21 financial year was New Zealand's hottest year on record, with most regions across the country reporting near-normal to above-normal rainfall levels. The following year set another record for the highest average temperature, with highly volatile rainfall. Several areas, particularly those on the North Island and upper sections of the South Island, reported above or well above average normal rainfall. In 2022-23, the North Island suffered catastrophic flooding events as well as severe damage inflicted by Cyclone Gabrielle, which devastated the Northern and Eastern Regions of the island. For the year through September 2025, the country continues to exhibit regional contrasts. Overall, IBISWorld forecasts annual rainfall will dip at a compound annual rate of 0.8% over the five years through 2025-26.