Cities worldwide categorize and name heat waves as temperatures soar—yours should too.
Arsht-Rock is working with international partners to pilot a heat-health warning system that categorizes and names heat waves. Unlike systems for other disasters, it is based on the expected negative health outcomes of the weather forecast specific to the cities involved, not just weather conditions alone.
Extreme heat has serious and under-recognized impacts on people and the places where they live, work, learn, and play. The move to categorize and name heat waves, as is done for hurricanes and other dangerous weather events, can help communities prepare for and respond to extreme heat and save lives. It is a critical step in enabling local authorities to better communicate heat risk, increase the flexibility of their emergency response, and highlight the human and economic damage caused by heat waves.
The Adrienne Arsht-Rockefeller Foundation Resilience Center (Arsht-Rock) is working with international partners to pilot an innovative heat-health warning system that categorizes and names heat waves. Unlike systems for other disasters, it is based on the expected negative health outcomes of the weather forecast that are specific to the cities involved, not just the weather conditions alone.
This article explains why cities around the globe are beginning to categorize and name heat waves to prepare for climate-driven extreme hea. It covers who is at risk from extreme heat and its effects, the current systems’ ability to capture these risks, and why heat waves should be categorized using a warning system based on human health outcomes.
Why categorize and name heat waves?
The consequences of extreme heat
Often referred to as the silent killer, heat waves do not provide the visual drama of wildfires’, hurricanes’, and floods’ infrastructural damage. Yet, they wreak damage on human and economic health, and awareness of this devastation is profoundly inadequate and out of date. Heat impacts our health and mental acuity, reduces worker safety and productivity, and decreases children’s learning. It lowers agricultural yields and food security, melts critical infrastructure, puts energy, electrical grid resilience, and greenhouse gas emissions goals at risk, and interrupts daily business and life in numerous other ways.
These impacts hurt people and economies, and there are few places safe from extreme heat. Temperate, unprepared regions will increasingly face severe heat waves due to climate change. For instance, over 1,000 people died of heat-related causes during a heat wave in the Pacific Northwest and British Columbia in June of 2021. Current heat warning systems do not fully account for heat’s risk to human health and need to be enhanced to meet the dire challenge of extreme heat.
Who is at risk?
Extreme heat is public health crisis, and everyone, everywhere can be at risk.
Certain groups, however, are more likely to face higher risks than others. Stories of elderly residents—particularly those with underlying health conditions—dying during seemingly harmless activities, like gardening, illustrate that just being outdoors can be dangerous during heat waves. Low-income people and communities of color often bear a disproportionate share of the burden, as they often lack access to cool environments, shade, and other resources to protect themselves from heat. People at higher risk of heat-related injury or death include:
- Outdoor workers and workers in hot or inadequately cooled environments.
- Elderly people, particularly those with underlying health conditions.
- Marginalized, informal, and low-wealth communities.
- Pregnant women, infants, and children, especially children under four.
But everyone is susceptible to heat-related illness. Recent research finds that younger people are susceptible to heat-related illness as well—no one is safe in the heat. Even on days that are not extremely hot, temperatures above the minimum morbidity temperature accounted for almost 12 percent of warm season emergency department visits for ages 0-18 in a sample of 3.8 million emergency department visits in 47 United States children’s hospitals. In August 2021, a young couple hiking in California died on the trail amid triple-digit temperatures, making headlines and underscoring the central contradiction: people do not perceive themselves to be at risk, even during life-threatening conditions. This is supported by focus group research that finds that people tend to think of others as vulnerable, but not themselves.
Closing the heat awareness gap
Despite the overwhelming evidence, public understanding of the risks of heat is low compared to other natural disasters.
Current heat warning systems do not fully account for heat’s risk to human health. Many are based on temperature or wet bulb temperature (a measure of the heat stress in direct sunlight, which takes into account temperature, humidity, wind speed, sun angle, and cloud cover), with sometimes arbitrary temperature cut-offs for a heat wave. These warning systems do not capture meteorological factors other than high temperatures that can harm people, such as the weather conditions in the 30 days before the heat wave. As a result, most current heat warning systems do not fully account for heat’s risk to human health and need to be enhanced to address the dangerous gap between the damage caused by heat and our awareness of the threat.
Why categorize heat waves using a warning system based on human health outcomes?
Categorizing extreme weather events using health-based metrics promotes better disaster preparedness and response, higher impact public messaging, and, ultimately, saved lives.
Meteorological terms such as heat index or wet bulb temperature can be complex and difficult to understand. Categorization using health-based metrics and improved public messaging are key steps towards helping local residents understanding the risks they face and delivering the protection they deserve. It also allows for more efficient and targeted allocation of government resources, and specific disaster preparation and messaging that can be scaled to meet the challenge of an upcoming heat wave.
Experience shows that when authorities base their heat warning system on health-based metrics like estimated mortality or morbidity and link effective communication and intervention strategies, they put people first and save lives. A 2018 study of heat warning systems in the United States found that the only city with a heat warning system that saves lives is Philadelphia, which uses a health-based metrics warning system.
Why name heat waves?
Hurricanes and other dangerous weather events are already frequently named, and this helps to sound the alarm on an upcoming public health emergency and build a culture of preparedness.
The naming of weather hazards improves clarity when communicating with the public, and research has found significant improvement in residents’ preparedness when storms are named.
Currently, heat waves are named in an ad hoc fashion for reference and archival purposes such as the 2020 “Labor Day Heat Wave” in California and the “Pacific Northwest Heat Dome” event of 2021.
When deadly heat waves are not named, as with the 2003 European heat wave that killed over 70,000 people, the dangers can be under-recognized. Heat waves should be named preemptively when a dangerous heat wave is projected, not after a deadly heat event ends. Doing so could help sound the alarm in advance and enable clearer communication with responders and the public.
How will the health-based forecasting system work?
Arsht-Rock and its team of experts analyze historical, locally specific weather conditions, and daily health and mortality data to develop unique algorithms that consider the region’s heat and health relationship. These algorithms allow jurisdictions to estimate the human health outcomes of forecasted weather conditions, providing advance warning for heat waves that are dangerous to human health.
This analysis allows us to categorize the severity of forecasted heat waves, giving officials an opportunity to provide citizens with effective and actionable recommendations that match the risks of projected heat. Some jurisdictions may also choose to name the most severe heat waves to further underscore the need for preparedness and response. In parallel, Arsht-Rock is developing recommendations to effectively message heat wave warnings and steps people can take to protect themselves.
More and more cities are working with Arsht-Rock to develop and implement health-based heat warning systems, including naming heat waves. In 2022, Seville, Spain launched a project to pilot Arsht-Rock’s heat wave categorization and naming systems; Athens, Greece also launched a pilot of Arsht-Rock’s categorization system. Further, Arsht-Rock is advancing efforts with Los Angeles County, California; Kansas City, Missouri; and Milwaukee and Madison, Wisconsin.