Marek Kučera 
New Zealand has experienced a burst of extraordinary winter warmth during the early July, with temperatures so mild they more closely resemble early summer than the heart of the Southern Hemisphere winter. From Auckland to the South Island, dozens of July temperature records have fallen, both by day and night.
In Auckland, daytime highs soared to a remarkable +21°C, while overnight minimums remained as warm as +15 to +16°C — temperatures far more typical of late spring or early summer. For perspective, average July lows in Auckland normally hover around 7–9°C, making these nighttime values exceptionally anomalous.
The warmth was not limited to the North Island. Even parts of the typically colder South Island saw nighttime minimums exceeding +10°C, a highly unusual occurrence for July, especially in inland and elevated areas where frosts are common this time of year. Many locations recorded their highest July minimums and maximums on record, reflecting the extent and magnitude of this warm spell.
The cause of this rare winter heatwave is a combination of subtropical air advection, a strong and stationary high-pressure system east of the country, and a persistent north-to-northwesterly airflow drawing warm, moist air down from the tropics. This setup also prevented typical nighttime cooling, especially under cloudy skies, leading to abnormally warm overnight temperatures.
Meteorologists describe the event as one of the most significant July warm anomalies in New Zealand’s recorded climate history, with daily temperatures running 6–10°C above normal in many regions.
While a short-term warm spell may feel pleasant, this kind of winter heat surge carries concerning implications. It can disrupt seasonal patterns in agriculture, affect ecosystems, and undermine snowpack accumulation in alpine regions. Several ski fields reported poor snow conditions and elevated snowlines, raising concerns for the rest of the winter season.
With global climate models projecting warmer and more variable winters, events like this are becoming more common in mid-latitude regions, including New Zealand. The early July 2025 warmth is a potent example of how climate variability and long-term warming trends are combining to reshape seasonal expectations — even in a country known for its temperate climate and meteorological stability.
Illustration picture: https://committeeforauckland.co.nz/2024-state-of-the-city-report/
