Niwa National Climate Centre forecasting principal scientist Chris Brandolino said the La Nina weather phenomenon would continue to have a meaningful influence on New Zealand’s climate in the coming months.
"Air pressure is forecast to be higher than normal over and to the south of the South Island, and lower than normal north of the country.
"This will likely result in an easterly quarter air flow anomaly and fewer westerly winds over the three months as a whole."
On the West Coast, the Alps and foothills, inland Otago and in Southland, temperatures were very likely to be above average, he said.
"More northeasterly winds and marine heatwave conditions will result in high heat at times."
Rainfall totals, soil moisture levels and river flows were about equally likely to be below normal or near normal.
"Early November will feature a band of heavy rain with the potential for flooding.
"However, over the season as a whole, more offshore winds will likely result in extended dry spells.
"Low rainfall may also occur around the hydro lakes."
Along coastal Otago, temperatures were also likely to be above average, he said.
"Fewer northwesterly winds may lead to fewer hot days above 25 degC, although more frequent northeasterly winds may contribute to more cloud cover and warmer overnight temperatures."
Overall, rainfall totals, soil moisture levels and river flows were equally likely to be near normal or below normal.
"Frequent anticyclones may contribute to long dry spells, increasing the risk for lower than normal soil moisture.
"These may be interspersed with moisture plumes that bring rain from the north."
Mr Brandolino said the changeable weather marked a period of "intra-seasonal variability", when weather patterns briefly diverged from the typical La Nina regime.
"This is expected to occur at times over the next three months."
