Has this been the driest January on the books?

Weather watchers will spend the coming days crunching numbers to see if this month's arid conditions break records - a prospect which could be doused by forecast rain for some places this weekend.

If none comes, however, 26 locations including South Auckland and Wellington could pencil in their driest January on record.

Yesterday, stations at Mangere, Wellington Airport, Dannevirke, Hawera and Kerikeri had recorded less than 5 per cent of normal rainfall for January. Whanganui had not seen a drop of rain, the city basking in a month-long dry spell.

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Niwa forecaster Chris Brandolino said the main reason for the unusually low rainfall was more high pressure systems than normal.

The month had been characterised by unusually warm mean maximum temperatures, Mr Brandolino said, but mean minimum temperatures had been "pretty ordinary".

"In other words, the overnight and early morning temperatures have somewhat offset the unusually warm days," he said.

This was due to a lack of cloud and dry ground, allowing heat which built up during the day to escape the earth's surface at night.

The warmest mean temperatures in the North Island this month had been recorded in eastern and northeastern parts of Auckland, northern parts of Coromandel, the Bay of Plenty, and the central and lower North Island.

In the south, much of Canterbury and northern Otago had seen warm mean temperatures.

And according to a climate outlook released by Niwa yesterday, the warm weather would carry on until April.

Temperatures would likely remain in the "above normal" range while soil moisture levels were likely to be near or below normal in the North Island and west of the South Island.

The MetService described January as a "very settled month", but reported that changes in weather patterns this weekend and next week could bring some much-needed rainfall and cooler temperatures.

While it was likely to stay dry at Eden Park today for the NRL Auckland Nines, there was the chance of an isolated shower and a bit of drizzle for eastern parts of Auckland tomorrow.