Record temperatures are being experienced in the South Island during a heat wave.
Warm air from Australia is sweeping across the country, with temperatures in Dunedin hitting a record 32 .7degC this afternoon. The previous December record is 32.2degC.
While the mercury in Ashburton has risen to 33.5degC, in Timaru it's 33.4degC and in Christchurch it's 30.1degC.
Gore has experienced an excessively warm night with temperatures of about 21.6degC to 22.6degC, MetService meteorologist Philippa Murdoch says.
It may be a record for the Southland town where the average December overnight temperature is 8.3degC, she told NZ Newswire.
"It's very sultry."
It is forecast to hit 35degC in Blenheim, which would surpass the previous best for December of 33.2degC in 1948.
It had reached 26degC in the Marlborough town in the early afternoon with hotter temperatures still expected.
Temperatures in the North Island are expected to be in the 20s.
On the downside, the heatwave with warm northwesterlies is increasing the fire risk in the east and the fire service is urging caution.
Rain and lower temperatures are forecast tomorrow, but conditions are expected to improve for Christmas Day with mainly fine weather across most of the country.