A powerful southerly storm swept across New Zealand this week, bringing torrential rain, damaging winds and mountain snowfall that triggered widespread flooding, landslides and major transport disruptions from the upper South Island into parts of the lower North Island.
The storm affected large areas between July 9 and 11, prompting MetService to issue multiple Severe Weather Warnings, including Orange Heavy Rain Warnings, as deep moisture combined with a vigorous southerly flow. The heaviest rainfall fell across eastern parts of the South Island, where moisture-laden air was forced upward by the Kaikōura Ranges, producing enhanced rainfall through orographic lifting.
Kaikōura was among the hardest-hit communities. Torrential rainfall caused both the Kowhai River and Lyell Creek to burst their banks, inundating homes, businesses and farmland while forcing hundreds of residents to evacuate. Although the district’s state of emergency has now been lifted, authorities continue to warn of an elevated landslide risk as saturated hillsides remain unstable.
The flooding left a lasting impact across the district. State Highway 1 suffered washouts, erosion and numerous slips, forcing several days of closures before authorities began reopening sections under reduced speed limits and stop-go traffic management. Two homes have been red-stickered because of landslide danger, while several more remain under restricted occupancy pending further geotechnical inspections.
The meteorological setup was driven by a vigorous southerly airflow transporting cold, moisture-rich air northward over the South Island. As the air encountered the region’s steep terrain, rainfall intensified rapidly. MetService forecast more than 130 mm (5.1 inches) of rain across parts of the northern Hawke’s Bay ranges under Orange Warnings, while areas inland of Kaikōura received more than 300 mm (11.8 inches) of rain during the event. At the Kaikōura coast, 137 mm (5.4 inches) was recorded, more than twice the area’s average rainfall for the entire month of July.
The severe weather extended well beyond Kaikōura. Rural communities across Marlborough became isolated after floodwaters, landslides and road washouts cut transport links. Ferry services across Cook Strait were cancelled because of rough seas, while Air New Zealand warned of flight disruptions as strong winds and poor visibility affected airports.
The storm also spread into the North Island. A state of emergency was declared in Wairoa after swollen rivers burst their banks under an Orange Heavy Rain Warning, forcing dozens of evacuations. More than 150 homes in the Gisborne region lost power as strong winds and saturated ground brought down trees and damaged electrical infrastructure.
Heavy snowfall affected higher elevations of the South Island as colder air wrapped around the southern side of the weather system, creating hazardous travel conditions across alpine routes while adding to the storm’s widespread impacts.
Although rainfall has eased across much of the country, authorities continue monitoring rivers and unstable hillsides. The Kaikōura District Council has warned that saturated slopes remain susceptible to further failures even after the heaviest rain has ended, while recovery crews continue clearing debris, repairing damaged roads and restoring access to isolated communities.
Looking ahead, conditions are expected to become more settled from July 14 as westerly winds replace the departing southerly outbreak. Temperatures will gradually recover across much of New Zealand, although a new band of rain is forecast to move onto the western South Island before spreading northward. MetService has also highlighted the potential for isolated thunderstorms and strong northwest wind gusts west of the Southern Alps, while recently flooded areas should remain alert as saturated ground could still lead to minor flooding or fresh landslides.
