Dunedin totally swamped its normal July rainfall record by 412% last month, and set a record of 235mm — the highest since records began in 1918.
Niwa climate scientist Nava Fedaeff said it was one of many rainfall records that toppled during the month, and was what made July 2022 "perhaps the most memorable" month of the year.
"From July 11-31, five separate weather events brought flooding rain to the country.
"The culmination of these frequent rain events led to 20 locations experiencing their wettest July on record and near-record wet months for a further 25 locations."
Setting new July rainfall records in the South were Dunedin Airport (143mm), Dunedin (Musselburgh) (235mm), Lauder (76mm) and Clyde (80mm).
Oamaru (193mm), Cromwell (76mm) and Nugget Point (156mm) recorded their second-highest rainfall totals.
Clyde and South West Cape also recorded their highest one-day rainfalls, with 26mm on July 18 and 111mm on July 26, respectively.
It was also New Zealand’s fourth-warmest July on record, with the nationwide average temperature reaching 1.3degC above average.
However, no temperature records were set in Otago and Southland. Rather, they were about average for July, she said.
"There was a multitude of drivers behind the wet and warm weather during July.
"The overall air pressure pattern saw higher than usual pressures to the northeast and southwest of the country and was associated with more northerly quarter air flows with warm and wet air mass origins.
"This dominant pressure set-up allowed for consecutive low-pressure systems to approach from the northwest which were supplied with flows of tropical moisture from the Coral Sea.
"The high pressure to the northeast of the country blocked the lows from moving away quickly and prolonged rainfall," she said.
This pattern was quite different from the southerly and southwesterly systems more characteristic of New Zealand winters.
La Nina continued to influence the climate system during July.
