The wet, warm July is proving to be one for record books

Aotearoa New Zealand just experienced its wettest — and fourth warmest — July on record, says NIWA.

A flooded street in Shirley, a Christchurch suburb, last month.
Photo: RNZ/Niva Chittock

In its monthly summary, the National Institute of Water and Atmospheric Research (NIWA) said that from July 11-31, five separate weather events delivered enough rain to cause flooding around the motu.

The peak of these frequent rains resulted in 20 centers experiencing their wettest July on record and record-breaking wet months for another 25 locations.

The vast majority of the country had well-above-average rainfall, with Wellington and Dunedin experiencing their wettest July on record, while Auckland and Hamilton experienced their second and third wettest July respectively.

A slip on Volga Street in the Wellington suburb of Island Bay.

A slip in the island bay after heavy rain in Wellington last month.
Photo: RNZ / Craig Stephen

The exceptions were coastal parts of Gisborne, Hawke’s Bay and North Wairarapa, which rained below normal rainfall.

It was the wettest month (of any month) in Christchurch on record. The 310mm of rain recorded there was the first time since records began in 1863 that more than 300mm of rain fell in a month. This was about half the rain the city normally received over the course of a year.

However, it was also warm, particularly in the North Island, where temperatures were well above average and many centers experienced record or near-record warmth.

Frequent wet weather meant it was also a cloudy month and this was reflected in warmer than usual overnight temperatures, with record or record-breaking high mean minimum (overnight) temperatures in both the North and South Islands.

Overall, it was New Zealand’s fourth-warmest July on record, with a nationwide average temperature (9.9C) 1.3C above average, NIWA said.

Some high-altitude weather stations, such as Mueller Hut (in Aoraki/Mt Cook National Park) on NIWA’s snow and ice network, recorded snow totals in July that were the highest for that time of year since records began in 2010.

NIWA said the wet, warm weather was the result of a general air pressure pattern that showed higher-than-usual pressures in the northeast and southwest of the country and was associated with air currents from more northerly quarters (origin of warm and humid airmass).

Council contractors clean stormwater drains in Edgeware, Christchurch, July 26, 2022.

Workers try to clean gutters at Edgeware in Christchurch during heavy rain last month.
Photo: RNZ / Niva Chittock

The prevailing pressure build-up allowed successive low-pressure systems to approach from the northwest, fed by tropical Coral Sea moisture currents.

High pressure in the country’s north-east prevented the lows from moving away quickly and resulted in sustained rains – a contrast to the southern and south-western systems, which are more characteristic of New Zealand winters.

La Niña also affected the climate system, bringing air currents to more northerly neighborhoods and contributing to warm sea surface temperatures that can help fuel incoming storms.

Other highlights:

  • The highest temperature was 22.6 °C and was recorded in Bromley on July 14
  • The lowest temperature was -11.6 °C recorded on July 17 at Aoraki/Mt. Cook measured
  • The highest 1-day rainfall was 371 mm on July 18 in Aoraki village/Mt. Cook recorded
  • The highest wind gust was 198 km/h and was observed on July 9 in Waipara West
  • Of the six main centres, Auckland was the warmest, Christchurch was the wettest, Hamilton was the driest, Tauranga was the sunniest and Dunedin was the coldest and least sunny
  • Of the available regularly reporting sunshine observatories, the four sunniest regions to date are Taranaki (1539 hours), Bay of Plenty (1478 hours), Greater Nelson (1462 hours), and Kāpiti Coast (1409 hours).
Niwa July 2022 weather information

Photo: Delivered / Niwa

Niwa July 2022 weather information

Photo: Delivered / Niwa

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