After a record warm May Northland is likely going to get a warmer than normal winter too.

The Climate Summary for winter, released by National Institute of Water and Atmospheric Research (Niwa) this week, predicts that Northland will have a milder than normal season, with temperatures likely to be above average but with rainfall also above normal.

Niwa looks at the probabilities - or per cent chances - for each of three categories: above average, near average, and below average.

In the absence of any forecast guidance there would be an equal likelihood (33 per cent chance) of the outcome being in any one of the three categories.

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Forecast information from local and global guidance models is used by Niwa to indicate the deviation from equal chance expected for the coming three-month period, with the following outcomes the most likely (but not certain) for Northland:

- Temperatures are very likely to be above average (80 per cent chance).

- Rainfall totals are most likely to be above normal (50 per cent chance).

- Soil moisture levels and river flows are most likely (45-50 per cent chance) to be in the above normal range.

The forecast follows Northland's warmest May on record with Whangarei, Kaitaia, Kaikohe and Kerikeri all having their highest ever mean maximum and minimum temperatures for the month.

Kaitaia recorded a mean maximum air temperature for May of 21.3C - 3C higher than normal for the month and the town's highest since records there began in 1948.

Kerikeri had a mean maximum of 21.2C, 2.6 above normal and the highest since records began there in 1981 while Kaikohe had a mean maximum of 19.9C, 3.1C above normal and the highest since records there began in 1973.

Whangarei, meanwhile, had a mean maximum of 20.8C, 2.7C above normal and the highest since records started in 1967.

All four centres also recorded their highest mean minimum temperatures ever for May, with Kaitaia at 13.7C (2.3C above normal); Kerikeri 12.1 (2.4C); Kaikohe 13.9C (3.3C) and Whangarei 13.4C (2.6C).