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Source: MetService

From tomorrow, 1 November and through summer, MetService will be issuing heat alerts.

This is the third year that MetService has been trialing alerts to help New Zealanders plan and prepare for extreme heat, alongside NEMA and our Civil Defence and Health partners.

This year, the influence of El Niño conditions across the Pacific is forecast to bring a hotter than usual summer across the eastern areas of Aotearoa New Zealand leading to additional concern in these regions.

Extreme heat during summer can be draining and have an impact on people’s daily lives – especially their health and wellbeing.

Everyone is vulnerable to extreme heat. However, babies, infants, older people and those with pre-existing medical conditions or on certain medications are more at risk.

International research shows that extreme heat and heatwaves can cause illness and death, but effective planning and actions can reduce its effects on health.

MetService meteorologist Georgina Griffiths says, “With extreme heat events worsening in response to climate change, a national heat warning system will be important to New Zealanders in the not-too-distant future. The trials undertaken over the last two years have served as a useful learning opportunity towards that goal.

Heat alerts will be displayed on the MetService Website and app for 46 towns and cities.

If a heat alert is triggered it means that people should take precautions, such as keeping hydrated, seeking shade, checking in with vulnerable people/children and looking after your pets and livestock.

People are also advised to use the alert information to inform their decisions, for example not going for a long run or having employees outside picking fruit.

What will trigger a Heat Alert?

“A heat alert will be issued for a town or city, if the forecast temperatures are expected to be unusual (very hot) for that location. This alerting scheme is not designed to capture every hot summer day, but rather focus on top end heat,” says Griffiths.

“Of course, the thresholds to trigger an alert vary a lot from one region to another – what is considered extremely hot for a Cantabrian is very different to what a Southlander will deem hot!”

MetService meteorologists have analysed weather information from 46 sites across New Zealand and created site specific thresholds for temperatures that are typically reached on average about once a year. A heat alert is issued if the forecast maximum for the day exceeds this threshold.

Additionally, this year, MetService will also be considering the minimum temperatures as well as the daily maximum.

“This additional factor will capture situations when overnight temperatures remain high, preventing suitable cooling from the extreme daytime heat. A heat alert will also be issued if two or more days exceed the threshold mean temperature,” adds Griffiths.

More information can be found at