The National Institute of Water and Atmospheric Research (Niwa) released its three-month summer forecast yesterday.
Across Southland and Central Otago, temperatures are very likely to be hotter than normal, with rainfall likely to be lower than typical levels, the report says.
Due to the La Nina global climate cycle, more offshore winds will likely result in extended dry spells in the region - which could include low rainfall at the hydro lakes.
More easterly winds and marine heatwave conditions will likely result in high heat and humidity at times.
"The region should remain aware of the potential for an ex-tropical cyclone or atmospheric river, particularly as La Nina eases over the next three months," the report warns.
Soil moisture and river flows in the region are expected to be either below normal or near normal.
In coastal Otago, temperatures are expected to be either near average or above average, while a decrease in northwesterly winds will likely lead to fewer days above 25degC.
However, more frequent onshore winds and marine heatwave conditions may contribute to increased cloud cover, warmer overnight temperatures and an increase in humidity.
Rainfall is expected to stay at or above average temperatures, with more frequent onshore winds potentially leading to more wet days.
Nearby anticyclones could increase the risk for dry spells, especially in the southern part of the region during mid-to-late January.
Soil moisture and river flows are expected to remain near normal levels.
