Source: NIWA
The Seasonal Climate Outlook for October – December is attached, along with graphics for your use.
– Moderate La Nina conditions continued during September and there was a strengthening marine heatwave (MHW). Both are expected to influence the climate over the next three months
– Air pressure is forecast to be higher than normal over the next three months, with the potential for longer dry spells in western areas
– Rainfall will be varied across the country, with the risk of the occasional sub-tropical to cause heavy rain in the north and east of the North Island
– Increased risk for early-season tropical cyclone activity in Southwest Pacific
– Temperatures are likely to be warmer than average across the country, with variability in October before a marked rise in November and December, along with an increase in humidity
More information about the marine heatwave:
– New Zealand’s coastal water temperatures remained above average during September, with anomaly values increasing in 4 out of 6 climate regions
– The MHW signal was amplified in climate model guidance issued in September, showing a sharp increase in SSTs from October-December
– Overall, it implies that MHW strength could rival that which was experienced in 2017-18 and 2021-22
– La Niña strengthened over the last two months and is very likely to continue over October-December
– This will likely culminate in the third La Niña summer in a row, a “triple dip” – while no two La Niña events are the same, there may be some similarities with last summer, which featured widespread hot and humid conditions, a marine heatwave, drought in the lower South Island, and several ex-tropical cyclones passing near New Zealand’s coasts
