Record low hit across the North

Northland's record July lows have seen frost across the region, and led to this spectacular icicle display on a farm fence on Hikurangi Swamp on Monday morning. Photo / Kasey Hindrup

Two Northland towns have recorded the lowest July temperatures on record- confirming suspicions that early mornings for the first half of this month have been especially chilly.

Figures released by the National Institute of Water and Atmospheric Research ( Niwa) showed this month's cold snap broke a swathe of temperature records around the country, including those in Kaitaia and Kerikeri.

More than 30 weather stations from Cape Reinga to Stewart Island had daily maximum temperature recordings that were either the lowest recorded, or at least in the top four coldest for July.

Kaitaia's lowest daily minimum was 0C on Saturday morning and Kerikeri's -0.7C on Sunday morning - both the lowest July temperatures since records began in 1948 and 1981 respectively.

Niwa climate scientist Gregor Macara said at the opposite end, the temperature in Cape Reinga was a comparably balmy 10.8C on Friday - the lowest daily maximum July temperature there since 1971. A July lowest daily maximum temperature was also recorded in Kaitaia at 9.6C.

Dargaville recorded the second lowest daily maximum at 9.4C since records there began in 1951.

The cold weather was caused by a cold southerly flow that brought icy showers and snow last week, followed by a high pressure system bringing clear skies and little wind to most of the country.

"Clouds act like a blanket at night and trap heat over the Earth's surface, whereas clear skies enable enhanced night-time cooling as this heat escapes the atmosphere. This process has contributed to the severe frosts observed lately," Mr Macara said.

He said the recent cold snap throughout the country was part of natural variability rather than any indication of a change in weather pattern. Record minimum temperatures, he said, in Kaitaia and Kerikeri were fairly uncommon.

"But they occurred on the back of an exceptionally cold snap when the entire country was hammered by frosts and given that Kaitaia had the lowest temperature on record shows temperatures there haven't been below zero."

"It appears frosts have been more severe this winter and that's being widespread in most parts of the country, even the top of the North Island," Mr Macara said.