Cloud makes summer month a little nippy

January 2012 was one of the coolest Januaries on record for Wanganui.

Cool, wet and cloudy is how Niwa climate scientist Georgina Griffiths summed up the month in the River City.

"It was very cloudy and the afternoons were not as hot and sunny as people would have liked or expected," Ms Griffiths said.

The mercury did not rise above 25C - recorded on the 10th - and the lowest January temperature was 6.1C, on the 28th.

But the real story was told in the average temperatures for the month, which were considerably lower than usual, Ms Griffiths said.

The average temperature for January was 15.8C - 2.5C lower than normal.

"That might not sound very much, but 2.5C is quite significant," Ms Griffiths said.

She said it was the third-lowest average January temperature in Wanganui since records began in 1937.

The mean maximum and mean minimum temperatures were also significantly lower than normal, with the mean maximum temperature of 19.6C the second-lowest since records began.

Ms Griffiths said Wanganui also received nearly 150 per cent of its average January rainfall - 90mm.

The average for January is 62mm.

Ms Griffiths said the whole country had been affected by unseasonable January weather she said.

"The pattern, generally, has been cool, wet and cloudy over much of the North Island and cool, dry and sunny over the South Island."

She said the cooler weather was caused by a predominance of southerly winds.

JANUARY WEATHER

Highest temperature: 25C, January 10

Lowest temperature: 6.1C, January 28

Average temperature: 15.8C

Total rainfall: 90mm