Niwa climate scientist Gregor Macara, of Lauder, said several periods of ‘‘exceptional warmth’’ resulted in summer-like temperatures in many areas, and dozens of locations had record or near-record-high daily maximum temperatures for the month.
He said April was characterised by lower-than-normal mean sea level pressure (MSLP) to the northwest of New Zealand, and higher-than-normal MSLP to the east of the country.
‘‘This produced more northeasterly airflows than normal, bringing sustained warm temperatures and several heavy rain events over the course of the month - including the arrival of ex-Tropical Cyclone Tam, in mid-April.’’
Among the 72 locations that had record or near record-high April mean temperatures were Franz Josef (14.0°C), Waipounamu (11.4°C) and Nugget Point (12.4°C), which had their second-highest April mean temperatures; and Oamaru (13.0°C), Dunedin (Musselburgh) (13.5°C) and Queenstown (12.8°C), which had their third-highest.
Of the six main centres, Dunedin recorded 160 hours of sunshine in April - the most sunshine hours in the country.
While it was not Dunedin’s driest April on record, the city only received 48mm of rain in the month - 79% of its normal April rainfall.
It meant Dunedin was the driest and sunniest of the six main centres, Auckland was the warmest, Christchurch was the coolest and Tauranga was the wettest and least sunny.
Mr Macara said the highest April temperature was 29.7°C, at Orari, on April 4.
But early in April, many southern records were broken when a warm northeasterly airflow covered the country on April 3, notably on Stewart Island where the temperature reached 25.9°C.
‘‘This was the highest April temperature observed at this location, exceeding the previous record by a remarkable 4.3°C.’’
On April 4, unusually high temperatures were also recorded in the South under a northwesterly airflow.
‘‘Most notably, Dunedin (Musselburgh) reached 29.5°C - this was the city’s highest April temperature since records began in 1947.’’
Middlemarch (28.0°C) and Nugget Point (25.0°C) also had their highest April temperatures on record, and Alexandra (28.4°C) had its equal-highest April temperature since records began in 1928.
Oamaru (27.3°C), Waipounamu (24.5°C), Cromwell (27.2°C) and Clyde (28.6°C) recorded their second-highest April temperatures.
Mr Macara said the nationwide average temperature in April was 15.2°C, making it New Zealand’s fifth-warmest April on record.
Rainfall was above normal or well above normal for much of the country, including Central Otago; and below normal or well below normal in Dunedin, South Otago and southeastern Southland.
By the end of April, soil moisture levels were below normal for South Otago and Invercargill.
