Up to 11 tropical cyclones could form across the Southwest Pacific this summer with at least four potentially reaching severe strength.
Earth Sciences New Zealand’s 2026/27 Tropical Cyclone Outlook forecasts between seven and 11 named cyclones from November to April, compared with a long-term average of about nine per season.
Principal scientist Dr Andrew Lorrey said El Niño conditions were influencing the outlook.
“During past strong El Niño events like the one that’s currently unfolding, we’ve typically seen elevated numbers of cyclones across the region, along with more activity to the east of the International Date Line. This is an area that’s usually fairly quiet,” he said.
El Niño is a climate pattern characterised by unusually warm ocean temperatures in the central and eastern tropical Pacific, which can alter weather patterns around the world.
Elevated cyclone activity is expected across the northern, northeastern and central Southwest Pacific.
Lorrey said there were also indications the cyclone season could begin earlier than usual.
“Over the long term, cyclone numbers have been gradually decreasing in the Southwest Pacific, but there can be prominent year-to-year variability.”
New Zealand’s overall cyclone risk remains normal, with the greatest risk in late summer and autumn, although a decaying storm may be more likely to affect northern or western areas than eastern regions.
“This year there is the potential that northern and western areas facing the Tasman Sea have more of a chance of experiencing a decaying storm than eastern regions,” Lorrey said.
“New Zealand’s most active months for ex-tropical cyclones are usually February and March, but some of them can visit us much earlier, and they can also occur beyond the end of April.”
In April, the remnants of Cyclone Vaianu brought destructive winds and heavy rain to the North Island, forcing hundreds of people to evacuate, leaving thousands without power and causing flooding and slips.
Meanwhile, at the other end of the Pacific, El Niño conditions and unusually warm ocean temperatures have helped fuel record-breaking hurricane activity in recent days.
In Mexico, at least six people have died after flooding and landslides caused by Hurricane Simon and the remnants of Tropical Storm Rachel.
Enormous waves associated with Rachel have battered the Southern California coastline, damaging beachfront homes and leaving 13 Long Beach homes unsafe to occupy.
The eastern and central Pacific have recorded their highest combined seasonal cyclone energy on record, surpassing the previous mark set in 2018.
“Communities across the Pacific should pay attention to forecasts and heed official advice if a weather warning related to a tropical cyclone is issued,” Lorrey said.