average weather south island new zealand january
January Weather in New Zealand â¦In the North Island, average top temperatures hover around 25Â°C dropping to lows of 12Â°C. And in the South Island, it's just slightly cooler with average top temperatures of around 22Â°C and lows of 10Â°C. (Do not be surprised by the odd really warm day with temperatures in the highâ¦.