As the globe warms, people will increasingly need affordable, safe methods to stay cool and minimize the worst health impacts of heat exposure. One of the cheapest cooling methods is electric fans. Recent research has recommended ambient air temperature thresholds for safe fan use in adults. Here we use hourly weather reanalysis data (1950-2021) to examine the temporal and spatial evolution of ambient climate conditions in the continental United States (CONUS) considered safe for fan use, focusing on high social vulnerability index (SVI) regions. We find that although most hours in the day are safe for fan use, there are regions that experience hundreds to thousands of hours per year that are too hot for safe fan use. Over the last several decades, the number of hours considered unsafe for fan use has increased across most of the CONUS (on average by similar to 70%), with hotspots across the US West and South, suggesting that many individuals will increasingly need alternative cooling strategies. People living in high-SVI locations are 1.5-2 times more likely to experience hotter climate conditions than the overall US population. High-SVI locations also experience higher rates of warming that are approaching and exceeding important safety thresholds that relate to climate adaptation. These results highlight the need to direct additional resources to these communities for heat adaptive strategies. Plain Language Summary As the globe warms, use of electric fans can help people stay cool if they can remain hydrated and if temperatures are low enough. Yet, there are limits to how hot it can be to safely use a fan because when temperatures are too high, a fan will increase the amount of heat traveling over the skin. We use data based on historical meteorological observations to study the number of hours in the continental US that exceed recommended temperature thresholds for safe fan use. We also examine where climate conditions considered unsafe for fan use overlap with socially vulnerable communities. We find that the geographic extent of temperatures too high for safe fan use is expanding, and the number of safe hours is decreasing. In the last two decades people have experienced double the number of hours with outdoor temperatures that are too hot for safe fan use compared to 50-70 years ago. Additionally, communities in socially vulnerable areas are experiencing higher rates of increases in unsafe hours than the overall population. Locations of particular concern include the southern and western US, highlighting the need to direct resources to invest in alternative forms of cooling in these regions.
Parsons, LA; Lo, F; Ward, A; Shindell, D; Raman, SR
Higher Temperatures in Socially Vulnerable US Communities Increasingly Limit Safe Use of Electric Fans for Cooling
Geohealth