Auckland (The NZ Today)
Aucklanders could be facing twice as many days above 25°C by the middle of the century, with new climate modelling warning that long spells of heat will become a much bigger part of the city’s summers.
An Auckland Council future urban heat assessment, issued on April 7, 2026, projects a sharp rise in both daytime and night-time heat as the climate warms.
At present, the modelling puts Auckland at an average of about 16 days above 25°C during the extended summer period.
By the 2050s, that could increase to around 31 days under a moderate emissions scenario and almost 40 days under a higher emissions scenario.
By 2090, the difference becomes much more dramatic — between 56 and 88 hot days a summer, depending on future greenhouse gas emissions. Under the higher-emissions scenario, that is more than five times the current level.
But the study suggests the bigger concern may not simply be individual hot days. It is how long the heat could stay.
Auckland’s longest daytime heatwaves currently average about four days. By the 2050s, they could last around seven days, while under the higher-emissions scenario the longest heatwave could stretch to about 21 days by 2090.
Nights are also expected to become considerably warmer.
The assessment projects a strong increase in hot nights and night-time heatwaves, reducing the opportunity for homes, streets and people to cool down after hot days. Under the highest scenario modelled, the longest night-time heatwave could reach around 33 nights by the end of the century.
The effect will not be the same everywhere.
Auckland’s built-up areas already experience an urban heat island effect, where concrete, asphalt and buildings retain heat. Earlier Auckland Council research found the city centre can remain up to 3°C warmer at night than surrounding rural areas.
That makes night-time heat particularly important for central Auckland and other densely developed areas.
While temperatures above 30°C are still expected to remain relatively uncommon, even the number of those very hot days begins to rise under the higher-emissions scenario towards 2090.
The findings are not simply about uncomfortable summers.
Auckland Council has previously warned that higher urban temperatures can worsen existing health problems, with older people, people with pre-existing conditions and communities facing economic hardship among those more vulnerable to prolonged heat.
The latest assessment says Auckland will need to factor rising heat into decisions about urban design, green spaces, trees and other infrastructure intended to cool neighbourhoods and make the city more resilient.
The projections are not a prediction that every Auckland summer will look the same. They show how conditions could change under different future emissions pathways.
But the direction across the scenarios is clear: Auckland is getting hotter, hot days are expected to become more common, and periods of sustained heat are likely to last much longer than the city is used to today.
Source: Auckland Council’s Auckland Future Urban Heat Assessment, prepared by Arup New Zealand.
