How Californians Tweet about Extreme Heat Events on Social Media: A Health Equity Perspective

Abstract Extreme heat events are increasingly common and deadlier than any other weather phenomenon, significantly affecting mortality rates. In California, these events have intensified, impacting populations differently based on structural factors of health and location. Tools like the healthy places index (HPI), which combines 23 social and economic indicators, can guide targeted heat mitigation efforts together with social media monitoring. We examined Twitter (X) heat discourse between 2016 and 2022 across California and by HPI. From keyword-filtered tweets ( n = 4572 in top 75th quartile HPI areas and n = 2701 in bottom 25th quartile HPI areas), we inductively identified eight heat discourse categories, listed in order of prevalence: perceived heat risk, life impact, coping, venting, heat warnings, community action, expressing relief, and climate change concern. Overall, extreme heat tweets correlated with heat events across these 7 years. Among high HPI areas, a greater proportion of heat tweets expressed positive sentiment, relief (when it cooled off), and coping. In contrast, among low HPI areas, a greater proportion of heat tweets expressed negative sentiment, venting, and heat warnings. Life impacts, perceived extreme heat, community action, and linking heat events with climate change were expressed with equal frequency across low and high HPI areas. Our results indicate that HPI serves as a robust geospatial heat equity tool for assessing extreme heat impacts across California and that extreme heat events are not experienced equally across communities. Significance Statement Increasingly, local governments are developing heat health action plans. A health equity lens recognizes that communities experience heat events differently depending on social determinants of health (e.g., housing, green space, air conditioning, income). Using the healthy places index (HPI), a composite measure of 23 community characteristics relevant to adaptive capacity to extreme heat events allows researchers to prioritize equity and measure how the most vulnerable communities respond to extreme heat. Communities in low HPI areas expressed greater negative sentiment and less coping. Social media monitoring of heat discourse by HPI provides real-time insight into heat risk experiences among the most vulnerable communities. Low HPI areas need to be prioritized for future public health research on adapting to extreme heat.