Just as the political climate is changing in New Zealand, so is the meteorological climate. It poses challenges that politicians, planners and voters alike cannot afford to ignore.
After years of being in varying degrees of La Nina, a strong El Nino phase has taken hold. It looks set to be the strongest El Nino in decades. The signature warming of the eastern Pacific Ocean, off the coast of Peru and Colombia is present. It shows the hallmarks of a particularly intense phase that is set to peak over the summer of 2026-27.
What has changed in the weather?
El Nino phases are a significant part of New Zealand weather. The prevailing westerly quarter winds strengthen in duration and intensity. This brings warmer than normal temperatures to eastern areas such as Canterbury, Marlborough, Otago and Hawkes Bay. The western regions, particularly Taranaki and the West Coast, can expect more rain and prolonged westerly quarter weather events. This trend is expected to dominate New Zealand weather over the remainder of 2026 and into 2027.
No one El Nino or La Nina is the same to the one that preceded it. Some El Nino phases have very strong westerly quarter winds. Others like the 1982-1983 phase have strong southerly influences. Not all bring large rainfall-bearing northwesterly to the West Coast. The 2007-2008 El Nino actually had a dearth of rain bearing events, and a stronger southerly influence.
“It is just the weather being the weather”
No. It is more complicated than “just the weather being the weather”. Big northwest rainfall events in July are rare. An event that drops 900mm in three days is an outlier even in summer. To have such a large event happen in the coldest month of the year is extreme.
Jim Salinger is a climatologist who used to work for N.I.W.A. He notes three drivers that can influence the nature of El Nino and La Nina. He says that the interplay between them determine how and where the effects of the El Nino will fall.
This year has not really been any different. In June a Metservice Red Warning was issued for the West Coast with 600mm of rain forecast across two days. The rain came, but impacted further north than forecast.
The weather is doing as the weather has done for millennia, but individual storm events are getting more intense. Conditions are changing from one extreme to the other more quickly. Individual events are occurring with less warning and change faster, making them more difficult for forecasters to accurately model.
This El Nino could be particularly stormy. The 1982-83 El Nino was notable in New Zealand for the strength of the thunderstorms that were spawned. They exhibited particularly strong tornadoes (including a very rare EF-3) and very damaging hailstorms. Thunderstorms caused significant localized flooding in Christchurch on at least one occasion in December 1983, and a tornado in Halswell at the start of that year.
It is also likely that there will be significant scrub and bushfires. Spring fed rivers frequently have little or no surface flow during summer, which reduces the available water for irrigation and fire fighting.
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