Dunedin, Oamaru, Wanaka and Alexandra all recorded their highest mean air temperatures for the month since records began.
Queenstown's figures were its second-highest on record, while centres further south, including Lumsden and Gore, also enjoyed July records.
Dunedin's mean temperature was 8.4degC, or 1.9degC above normal, while Wanaka's was 6.4degC (3.1degC above), Cromwell's 6.1degC (2.9degC above) and Alexandra's 5.8degC (2.8degC above).
In Dunedin, the mild weather came with another bonus, only about half the city's normal monthly rainfall - just 33mm, 1mm more than Auckland, which had its second-lowest July rainfall on record.
Across the country, Niwa's July climate summary showed New Zealand recorded its fourth-warmest July on record.
In the South Island, mean temperatures were more than 1.2degC above average, with many places in Canterbury joining Otago in recording record July mean temperatures.
Principal scientist Andrew Tait said July was characterised by much higher pressures than normal over and to the north, east and west of New Zealand combined with persistent lower pressures well into the south.
It also created dry conditions in the northern half of the North Island, and eastern South Island, for example, Oamaru airport recorded only 3mm of rain, its fourth-lowest total since 1898.
Queenstown recorded its second-highest sunshine hours since 1930 with 125, just short of Dunedin's 130 hours which was just above normal. Hamilton was the cloudiest city, with 120 hours of sunshine.
Otago soils were wetter than normal because of high June rainfall, Dr Tait said.
| For the record | ||
| Record mean maximum July Temperatures | ||
| Mean maximum | Above normal | |
| Dunedin Airport | 12.7° | 2.3° |
| Musselburgh | 12.5° | 2.5° |
| Queenstown | 10.6° | 2.9° |
| Cromwell | 11.6° | 3.6° |
| Wanaka | 10.9° | 3.3° |
| Alexandra | 11.5° | 3.5° |
