Alex Macmillan, a senior lecturer in Environmental Health at the University of Otago, urged people to "take care" in the extreme heat, "especially if you’re elderly, pregnant, or already have a medical condition". "As year on year we break new heat records as a result of our collective failure to act on climate change, New Zealand urgently needs a climate change and health adaptation plan, so that we can ensure people’s health is protected from the impacts of climate change, including these higher summer temperatures," Dr Macmillan said. "The good news is that by investing now in well-designed climate action, including homes and public buildings that are easy to cool without fossil fuels, and better city planning, we can stay healthier and more resilient to heat events like this, and reduce our climate pollution at the same time." Why is it so hot? Take several helpings of hot air from Australia and the sub-tropics, some long and sunny days, warm ground, New Zealand's mountains, and a nearby anticyclone accompanied by light winds, and you have the recipe for this week's heatwave.

Usually, a very warm air mass from the Australian outback would be cooled significantly by contact with the Tasman Sea as it moves across to New Zealand. However, this summer, with another marine heatwave under way and sea-surface temperatures in parts of the Tasman up to 4 degrees warmer than average, that modifying influence on the lowest layers of heated air has been significantly reduced. How much this particular hot spell can be sheeted home to climate change is difficult to quantify. But the marine heatwave - for the second consecutive summer - is perhaps the clearest indicator of such change.