A summer heat alert trial has been launched to warn more New Zealanders of unusually hot weather.

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

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

'With extreme heat events worsening in response to human-induced climate change a national heat alert system is really important – this trial is an important step towards that,” says MetService meteorologist Georgina Griffiths.

'Last summer we ran the first phase of the heat alert trial - the first of its kind in New Zealand.

'This summer, through until 30 March 2023, we're expanding the trial by doubling the locations the alerts are provided for and refining the alert thresholds.”

The heat alerts will cover 44 urban areas that MetService write a daily forecast for.

An alert will be triggered by an extremely high temperature (record or near record) or when a run of very hot and humid weather is forecast.

Hot, humid weather is typically less well tolerated than hot, dry weather.

Heat alerts will appear on metservice.com, and in the new year on the MetService weather app, in a banner and as part of the daily forecast for each location.

An example of what the alert will look like on the MetService website.

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.

'New Zealand, unlike countries such as the United Kingdom and Australia, does not have a national heat warning system.

'This heat alert trial is an opportunity to look deeper into the New Zealand requirements of such a warning system.”

MetService are, again, providing heat alerts direct to Te Mana Ora Waitaha Canterbury (formerly Community and Public Health, Canterbury DHB) and this year will also be provided to the Auckland Council.

The criteria for the alerts were developed by meteorologists at MetService and Dr Luke Harrington Senior Lecturer in Climate Change at the University of Waikato

'The thresholds for the alerts are localised to the area in question – the threshold for Northland or Gisborne will differ from that used in cooler areas, such as Westland,” says Dr Luke Harrington.

'Thresholds to trigger alerts have been set very high, in part to ‘future proof' this type of alerting against a background of continued warming due to climate change.”

Luke recently undertook a synthesis of extreme heat in New Zealand. Results showed the hottest days of the year have warmed by more than half a degree over the last 20 years for many populated regions of the country, a rate which exceeds average annual changes across the country.

'We've had some record-breaking summers in recent years These alerts are for extreme heat and we'd only expect to use them occasionally,” says Georgina.

'How often the alerts are issued, of course, depends on the type of summer we get! December has started off cooler than usual so far, but La Nina should kick in, producing above average summer temperatures, overall.”