[These comments on the availability of NZ temperature records from the ever-watchful Warwick Hughes in Australia may draw useful information from someone.]
The headline in The NZ Herald says New Zealand hit by record cold temperatures overnight, yet a reading of the article gives no examples of actual records, only some bone-chilling -20°C overnight lows in the South Island. Hopefully some Kiwis might have better information.
The Met Office over there and NIWA have very poor online data sources to check weather history. The Australian BoM is light-years ahead with their website.
Kiwis who are interested in weather history would be better served by the NZ weather authorities abandoning their pitiful website efforts and contracting that weather history stuff out to the BoM.