Heat planning must account for asthma and chronic respiratory illness, the World Health Organization warned in updated guidance that treats extreme temperatures as more than a risk of dehydration or heatstroke.
The agency’s Heat and Health fact sheet, updated July 31, calls heat stress a leading cause of weather-related deaths and says it can exacerbate asthma and worsen chronic respiratory conditions. WHO estimates that approximately 489,000 heat-related deaths occurred annually from 2000 through 2019, while heat-related mortality among people older than 65 rose about 85 percent between 2000–2004 and 2017–2021.
For people with breathing disorders, the risk often comes as a stack rather than a single hazard. High temperatures place additional strain on the heart and kidneys, while hot days may coincide with particle pollution or other poor-air episodes. Extended hot days and nights also create cumulative stress by reducing the opportunity to recover in a cooler environment.
The U.S. Centers for Disease Control and Prevention makes the compound-risk connection more explicit. Its clinical guidance on heat and childhood asthma notes that hot weather can raise ozone and particle pollution and increase wildfire risk, while smoke, pollen and mold can add respiratory
triggers. The combination means a temperature forecast alone may not be enough to guide outdoor work, exercise or children’s activities.
WHO identifies older adults, outdoor and manual workers, athletes and people with inadequate housing or limited access to cooling among those facing elevated risk. Vulnerability depends on health and medication use, but also on working conditions, social isolation, electricity, building quality and whether a person can reach a cool space. A regional forecast may also conceal hotter urban neighborhoods.
The public advice is direct: follow official warnings, avoid strenuous activity during the hottest part of the day, spend time in a cool place and keep the body cool. Hydration should follow individual medical guidance, particularly for people whose heart or kidney conditions require fluid restrictions. Confusion, fainting or suspected heatstroke is an emergency.
The update also shifts responsibility toward public systems. WHO promotes heat-health action plans, early-warning systems and protections for workers and vulnerable groups. Its second-edition guidance for heat-health action plans, released in June, emphasizes coordinated preparation across health services and local authorities.
The practical summer check is therefore broader than “How hot will it be?” It includes humidity, air quality, overnight temperatures and reliable access to cooling. For people with asthma or other chronic respiratory conditions, those combined conditions can determine whether an ordinary day outdoors becomes a breathing risk.
