Agriculture Minister Damien O'Connor has asked officials to keep a close watch on how farmers and growers are managing in dry conditions, as the hot start to summer affects soil moisture levels across the country.

"Farmers and growers in many of our regions are experiencing lower than normal soil moisture levels for this time of year," O'Connor said.

Niwa meteorologist Chris Brandolino said below normal rainfall was expected for most of New Zealand for at least the next 10 days with perhaps only localised exceptions.

"It's distinctly possible that much of the country will experience below normal rainfall through to the Christmas holiday period, and December temperatures are very likely to remain above average for all of New Zealand and the summer season as a whole."

Particular hotspots are found across Hawke's Bay, in parts of southern Manawatu-Whanganui, northern Waikato and Wellington-Wairarapa; hotspots are developing across much of the South Island with the exception of parts of Central Otago due to last week's thunderstorms.

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Drier-than-normal weather is already translating into higher dairy futures and wholesale electricity prices.

Niwa said a "powerful and persistent" ridge of high pressure over much of New Zealand during the second half of November caused near-record or record dryness in some locations and has led to the depletion of soil moisture levels with plants in some areas in the lower North Island and South Island approaching their "wilting" points.

Bank of NZ senior economist Doug Steel said last week that the bank had not adjusted its economic forecasts on account of the spreading dry.

Agriculture Minister Damien O'Connor has asked officials to watch how farmers manage the current dry conditions. Picture / NZME
Agriculture Minister Damien O'Connor has asked officials to watch how farmers manage the current dry conditions. Picture / NZME

"But it is a risk worth highlighting, especially with near term weather forecasts showing little rain on the horizon," Steel said.

"If dry conditions persist for too long, we would expect GDP to be lower than currently expected."

ASB Bank said it was maintaining its production forecasts for now.

The bank said its nationwide milk production growth forecast for this season, for example, still stood at 3 per cent.

"However, if the dry weather continues for the rest of December, we will revise down this forecast. Indeed, many NZ farmers will be anxious for rain over coming weeks," the bank said.