Bay of Plenty's winter months are looking reasonably warm and dry, though experts forecast the occasional cold snap and frost to pass through.

The National Institute of Water and Atmospheric Science's seasonal climate outlook for June, July and August shows a warm quarter with near or above average temperatures.

Photo: File.

A continuation after sunshine for the month of May was abundant in the Eastern Bay of Plenty, and other eastern parts of the country, typically above normal, 110-125 per cent, or well above normal, above 125 per cent.

NIWA meteorologist Chris Brandolino, in the report's summary, says international guidance indicates that El Nino conditions are very likely, 90 per cent chance, to continue during the next three months.

The likelihood of El Nino persisting or strengthening as we reach into spring is also very high, above 80 per cent.

El Nino is typically associated with stronger and/or more frequent westerly winds, leading to drier conditions in eastern and northern areas and more rain in western areas.

'During June – August 2015, above normal pressure is forecast to the west of New Zealand, while below normal pressure is expected to the northeast of the country. This circulation pattern is likely to be accompanied with anomalous westerly to southwesterly wind flows,” says Chris.

He says all regions of New Zealand except in the north of the North Island will experience near or above average temperatures during this time.

Rainfall totals are about equally likely – a 35-40 per cent chance – to be in the near normal or below normal range for all regions of New Zealand except for the west of the South Island, where near normal rainfall is the most likely outcome.

Air temperatures are equally likely to be average or above average in all regions of New Zealand except in the north of the North Island, where temperatures for the next three months as a whole are most likely to be in the near normal range.

Chris notes that cold snaps and frosts are to be expected in some parts of the country as we progress into winter.

Looking back on the month of May, Chris says it was characterised by air pressures which were well below the normal in the Tasman Sea, with below normal pressures extending over the country.

The month was characterised by abundance of sunshine for most of the eastern parts of the country, including the Eastern Bay, along with heavy rainfall.

Rainfall was well above normal, greater than 149 per cent, or above normal, 120-149 per cent for the eastern parts of the country.