Unfortunately, Earth Sciences New Zealand (ESNZ) forecasting principal scientist Chris Brandolino said it was likely to rear its ugly head again this month.
He said October’s harsh conditions were caused by a "minor sudden stratospheric warming (SSW) event" which developed over Antarctica in September 2025.
The impacts of the SSW near the top of the atmosphere, propagated downwards through the troposphere where our weather occurs, greatly influenced the unsettled conditions throughout October.
"While a transition to other climate drivers, like La Nina, is expected over the next three months, the SSW may continue to influence conditions during November.
"[Which] will begin with the first period of prolonged, settled weather this spring, as an anti-cyclone [high-pressure system] dominates.
"However, it’s likely this will not prevail throughout the entire month, with probable periods of rain from both the north and west.
"Despite this, a dry lean for the month is expected for most areas, with only the northern North Island at particular risk of running wetter than normal for the month."
Mr Brandolino said La Nina conditions had now emerged in the tropical Pacific and forecasts from ESNZ’s Relative Oceanic Nino Index indicated a high probability of La Nina conditions prevailing during the November 2025 to January 2026 period.
From mid-December through to the end of January, high pressure was expected to sit more frequently over, or south of, the South Island, resulting in an easterly quarter anomaly airflow over the country.
Westerly fronts should be reduced in frequency and there was an elevated risk of lows from the north drifting on to the country.
As a result, temperatures on the West Coast, Southern Alps and foothills, inland Otago, and Southland were most likely to be above average; seasonal rainfall totals were about equally likely to be near normal or below normal; and soil moisture levels and river flows were most likely to be near normal, he said.
Along coastal Otago, temperatures were about equally likely to be above average or near average; rainfall totals were most likely to be near normal; and soil moisture levels and river flows were about equally likely to be below normal or near normal.
