New research shows some US areas are reaching dangerously hot temperatures that exceed fan safety thresholds nearly double the amount from decades past.
Analyzing hourly weather data from 1950–1969 and the past 20 years, Duke University’s Luke Parsons found more residents face heat levels too high for electric fans to effectively cool them.
In locations like inland California, central Texas and Oklahoma, and along the US-Mexico border, conditions often surpass thresholds for safe fan use even for healthy young adults. These hotspot areas now experience over 1,000 hours—over 44 days—per year of fan-unsafe heat, rising by 200 hours compared to 50–70 years ago.
Electric fans can still be used up to 95°F but limits depend on humidity, age and health. At over 100°F, fans may exacerbate heat stress for older adults or those on medications affecting sweat. The vulnerable communities most impacted with limited means to cope merit resource directing, scientists stress.