Niwa climate scientist Gregor Macara said the mean sea-level air pressure was higher than normal to the south and east of the South Island, and lower than normal to the west of New Zealand.
"This was associated with more northeasterly winds than normal for the month overall, which was consistent with a trend toward La Nina-like conditions in the tropical Pacific," Mr Macara said.
"The lack of cold southerly airflows contributed to a warm start to winter for most of the country.
"Temperatures were above average for all the main centres.
"It was especially warm in Dunedin, with the city observing its third-warmest June on record."
On June 1, a strong and warm northerly airflow covered much of the South, bringing "exceptional warmth", he said.
As a result, Waimate recorded its highest June daily maximum air temperature when the mercury reached 23.4°C; and on the same day, Oamaru recorded its second highest (22.2°C), and both Dunedin (Musselburgh) and Cromwell recorded their third highest, with 20.3°C and 19.3°C, respectively.
However, there were isolated pockets of near-average temperatures in parts of inland Southland and Otago.
Overall, the nationwide average temperature in June 2024 was 9.9°C — making it the 12th-warmest June since Niwa’s seven-station temperature series began in 1909.
Hastings recorded the highest temperature (25.7°C) of the month on June 10, which was also New Zealand’s highest temperature on record for June.
The lowest temperature in New Zealand was -9.4°C, in Middlemarch, on June 12 — the fourth-equal lowest on record.
Rainfall was below normal or well below normal for the West Coast, western Otago, eastern Southland, and Fiordland.
Mr Macara said the lack of rainfall contributed to below normal inflows for the Waitaki and Clutha hydro lakes.
Rainfall was above normal or well above normal in eastern Otago, and near normal for the remaining areas of the southern regions.
Roxburgh posted its highest June extreme one-day rainfall total when 31mm fell on June 15, and on the same day Tautuku posted its second-highest, when 45mm fell.
Soil moisture at the end of June was lower than normal for much of inland Otago and the lower West Coast, but it was near normal for the rest of the southern regions.
Extreme wind gusts on June 1 also set new records when Wanaka winds reached 82kmh and South West Cape had 170kmh.
Ranfurly recorded its second highest with 90kmh, while Manapouri (70kmh), Lauder (111kmh) and Clyde (75kmh) recorded their third highest.
