Niwa's outlook says that international guidance shows the chance for weak El Nino conditions between January, February and March stood at a 70 per cent chance of happening.
The El Nino conditions can mean for heavy rain and tropical weather.
This month is expected to bring warmer than usual temperatures -- with a 45 per cent chance of above normal temperature ranges in the west of the South Island and between 35-40 per cent chance of near normal or above in other parts of the country.
Soil moisture levels are "most likely" to be below normal in the east of the South Island, while river flows have a 50 per cent chance of being below the usual flow in that part of the country.
In terms of rainfall, there is up to a 40 per cent chance of this being near-normal or above normal in parts of the North Island.
Most of the South Island is thought to be in for near-normal or below normal rainfall (40 per cent chance), while near-normal rainfalls are expected in regions at the top of the South Island.