The Waikato region is likely to enjoy a warmer winter with El Nino conditions ''increasingly likely'' this year.
The National Institute of Water and Atmospheric Research (Niwa) has issued a seasonal climate outlook for the weather patterns over the next three months.
The outlook suggested Waikato, Bay of Plenty, Northland and Auckland would all have a 40 to 45 per cent chance of average or above-average temperatures during the May to July season.
Rainfall totals were likely to be in the near normal range while soil moisture levels and river flows were equally likely to be in the normal or below normal range.
Niwa said for 16 consecutive months, the sea had been warmer than normal. Winter temperatures were likely to be normal or slightly higher than normal for most parts of the country.
''El Nino is coming, just not quite yet,'' the outlook said. ''Despite a lot of recent rain, soil moisture levels are still well below normal in parts of the country. From May to July average temperatures were most likely for the west of the South Island and above average temperatures were exdhpected for the east of the North Island.''
The outlook said people should not ''go ditching the winter woollies yet''.
''Cold snaps and frosts can still be expected in some parts of the country as autumn advances into winter,'' it said.
Niwa said above-normal sea surface temperatures along the equator now covered a significant part of the central and far eastern Pacific, and the warm anomalies were consistent with developing El Nino conditions.
It said 11 of the 14 models it monitored were predicting El Nino conditions in August, September and October.
For New Zealand, that usually meant stronger or more frequent winds from the west during summer.
That could lead to drought on the east coast and more rain in the west of the country.