Heatwaves show importance of health early warnings and action plans

18 July 2023

The World Meteorological Organization is stepping up efforts to strengthen heat-health early warnings and integrated action plans for heatwaves, which are amongst the deadliest natural hazards. Heat is a rapidly growing health risk, due to burgeoning urbanisation, an increase in high temperature extremes, and demographic changes in countries with ageing populations. Hundreds of thousands of people die from preventable heat-related causes each year.

Global temperatures have been at unprecedented levels for several weeks. The extensive and intense heatwaves this year are alarming, but not surprising because unfortunately the conditions being observed are in accordance with projections from the Intergovernmental Panel on Climate Change.  

The impacts on people, economies, and the natural and built environment are serious.

new study published last week, calculated last summer in Europe alone 60,000 additional people died due to extreme heat. Experts and governments consider this a conservative estimate. And it is worth noting, the figures are for Europe, which has some of the strongest early warning systems and heat-health action plans in the world,” said Joy Shumake Guillemot, of the World Meteorological Organization/World Health Office joint office on Climate and Health.

Current situation

There is currently a simultaneous heatwave phenomenon occuring, with temperatures in North America, parts of Asia, and across North Africa and the Mediterranean above 40°C for a prolonged number of days this week. These types of events are very concerning and have increased sixfold since the 1980s.

The recently declared El Nino is only expected to amplify the occurrence and intensity of such extreme heat events and impacts on human health and livelihoods

On the weekend of 15-16 July, the US National Oceanic and Atmospheric Administration (NOAA) said excessive heat warnings and advisories covered more than 100 million people in the United States with “dangerous and swelting heat” especially across much of the Western USA.

Areas at risk in the southwestern USA include California, southern Nevada and Arizona.  In South-Central and Southeast USA, maximum heat index values could near or exceed 110 ° Fahrenheit (43° C). For instance, Phoenix, Arizona, has suffered an extended streak of exceptionally high temperatures. That will continue, with day time maximum temperatures of at least 116°F (46.7°C) until Friday 21 July and overnight low temperatures of more than 90°F (32.2°C), according to the US National Weather Service.

Overnight minimum temperatures are expected to reach new highs. This is concerning because repeated high night-time temperatures are particularly dangerous for human health because the body is unable to recover from hot days, leading to increased cases of heart attacks and death. Whilst most of the attention focuses on daytime maximum temperatures, it is the overnight temperatures which have the biggest health risks, especially for vulnerable populations.

“We need the world to broaden its attention beyond the maximum temperature alone. In many locations where the maximum is reaching into the high 40°Cs and higher, the temperature may still be near 40°C at midnight. In these circumstances, the minimum temperature is more important for health and failing critical infrastructure during extreme heatwaves,” said senior WMO extreme heat advisor John Nairn.

“Worldwide, more intense and extreme heat is unavoidable – it is imperative to prepare and adapt as cities, homes, workplaces are not built to withstand prolonged high temperatures – and vulnerable people are not sufficiently aware of the seriousness of the risk heat poses to their health and wellbeing,” said Dr Nairn.

Tried, tested, and iteratively updated response strategies and communication plans are needed to target both the general population and vulnerable groups such as older adults or outside workers; displaced and marginalized populations.

WMO response

how can you beat heat?.

WMO, through the Early Warnings for All Initiative is strengthening member capacity to develop and deploy impact-based warnings.  This includes updating guidance on heat health warning systems; and developing standardized terminology and definitions for extreme heat. Harmonized approaches and categorization of heatwave intensity will standardize and help scale up the implementation of impact-based forecasts and warnings worldwide.

Various WMO programmes support research on extreme weather and urban heat and promote the global scale up of protective policies such as heat action plans that incorporate early warning and response systems that target vulnerable people and critical supporting infrastructure.

WMO has also partnered widely on the topic of extreme heat and is working with the World Health Organization, academic and governmental and non-governmental partners through the Global Heat Health Information Network as well as the WMO/UNDRR Center of Excellence.

WMO Position on Heatwave Naming:

WMO has no immediate plans to engage in heatwave naming.

The WMO Services Commission, comprised of 121 governments, considered the issue in October 2022 and there was unanimous agreement on the need for caution.

Members requested WMO to focus attention on strengthening authoritative heat-health warning systems, enhancing technical heat forecasting capabilities, and building capacity and partnerships to protect vulnerable communities from extreme heat. Key considerations and findings are summarized in a Technical Brief.

Naming heatwave events puts focus on the wrong issues. Naming singular heatwave events misdirects public and media attention away from the messages that matter most, which are who is in danger and how to respond. This practice can create confusion in risk communication messaging and distract the attention of authoritative partners from implementing heat warning systems and responses.

WMO coordinates the international naming system for tropical cyclones, which are clearly distinguishable, trackable and predictable weather systems. What has been established for tropical cyclone events is not necessarily appropriate for or translatable to heatwaves.

  • There is no standard classification or ranking system for extreme temperature events, including heatwaves. The practice of decoupled naming and early warning, as well as inappropriate naming, could bring unintended negative consequences and reduce the effectiveness of established heat advisory and response measures.
  • The additional act of “naming heatwaves” does not assist with the identification or characterization of extreme temperature events.
  • The time burden for NMHS, health authorities and other civil protection authorities to engage with a naming scheme, including its coordination and providing technical clarifications to other civil authorities, and the media will detract staff focus from providing official EWS/advisory services and life-saving interventions

Technical brief on heatwave naming is here:

Further Resources:

Press Package Reporting on Extreme Heat and Health: https://ghhin.org/press/

WHO Heat Safety Messages in 18 European Languages: https://who.canto.global/v/V6BJQPBKL4/album/PQCBG?viewIndex=0