“When there's a deep depression in the eastern Tasman Sea and a large anticyclone east of New Zealand, it creates a strong northerly flow of moist air,” he said. “That’s what we’re seeing now.”

The MetService pressure map for Friday, July 11, showed precisely this setup. The northern regions of the South Island are particularly exposed to such northerly systems while being sheltered from the south and west.

“This kind of pattern increases the odds for big rainfall events,” Brandolino said. “We’re in one right now, and it looks set to continue.”

But the current back-to-back storms have overwhelmed local catchments, with rainfall setting records since late June.

The saturated ground means new rain has nowhere to go, quickly swelling rivers and flooding roads and homes.

The NIWA Climate Outlook for July to September warns of further tropical and sub-tropical influences, increasing the risk of heavy rainfall and flooding.

“There’s a high likelihood for these kinds of low-pressure systems to keep affecting New Zealand,” said Brandolino. “This may mean more active weather toward the end of July and even into early August.”

“This is the third event in just over two weeks,” said King. “The community is resilient, but we’re exhausted—and still in the thick of it.”

Read More News on