The heatwave New Zealand is experiencing has the country on track for the hottest month since records began in 1909.
Oriental Bay, Wellington Photo: RNZ/Karen Brown
The current record for the hottest ever month is an average 19.61 degrees Celsius set in February 1998.
Niwa meteorologist Ben Noll said with warm weather predicted until the end of the month, that record was under threat.
"So far in January 2018 we're tracking in the first 23 days at [more than] 19°C."
Data collected by Niwa's nationwide seven-station series showed January was also likely to break the record for warmest month compared to normal.
The current record is from December 1934, when the national average temperature was 2.67°C hotter than normal.
"January 2018 is warmer than that," Mr Noll said.
"So far the temperature is tracking on average to be warmer than 2.7°C above the long-term average.
"It's close to 3°C above the long-term average, so that's quite a significant number when you get to be several degrees above average in terms of a nationwide temperature."
MetService meteorologist Tui McInnes said the hottest places today would be in the Wairarapa and Central Otago.
"We've got forecast 33°C in Masterton and 33°C in Alexandra, so they would be the two hotspots."
Temperatures were likely to edge up further early next week, especially in the South Island, Mr McInnes said.
"For example, in Alexandra we're looking at the mid-30s, possibly, on Monday. The same with Wanaka ... and in places a bit further south like Gore and Invercargill."
A warm, humid ridge that had been sitting over the country since the beginning of the week was exacerbating the high temperatures, Mr McInnes said.
Climate Change Research Institute director Dave Frame said more indepth research was needed to measure the impact of climate change on the weather.
"Here in New Zealand, mostly science means field science, so people going out and taking observations and measurements and analysing those," he said.
"What you need to do to understand the overall effect on our climate is to model it ... and that's not an area New Zealand's usually invested in."
Heating up
- The current record for hottest January is 19.01°C in 1956 (which is 1.88°C above normal for January).
- For January 2018 so far (1-23 Jan), the mean temperature is 19.85°C (2.72°C above normal).
- The current record for hottest ever month is an average of 19.61°C in February 1998. January 2018 is on track to surpass this.
- The current record for warmest month compared to normal is +2.67°C in December 1934. January 2018 is on track to surpass this too.
