Real-World Physiological Experiences of Cooling Center Users and Cooling Efficacy: A Phoenix Case Study

Background: Cooling centers are critical resources for protecting the public from extreme heat and its adverse impacts. However, evidence regarding the effectiveness of brief or longer-term use of cooled spaces is lacking, as is information on the physiologic states of those coming to use cooling or respite centers. Users of these spaces often ask how long they must stay within the cool environment to recover from prolonged heat exposure, a question that lacks evidence and depends on many personal and behavioral factors (health status, time in the heat prior, condition entering the cooling center, etc.).

Objectives: To understand 1) the physiologic state of individuals entering a cooling center after continued heat exposure; 2) the duration to return to a safe physiologic baseline; and 3) the indicators of vulnerability connected to hydration, health, and time-activity patterns in the heat.

Methods: We conducted surveys and physiologic assessments of 42 subjects in the summer of 2024 at one respite center in Phoenix, AZ. Participants were >55 years of age and were experiencing unsheltered homelessness. Core temperatures, skin temperatures, blood pressure, and hydration status were measured throughout a 2-hour period after entering the respite center in downtown Phoenix. A short survey was also administered.

Results & Discussion: All subjects in the study presented with heat stress (higher body temperature, self-reported heat stress symptoms) in the morning at the respite center. Approximately half of the participants had slept outdoors the previous night. On average, participants returned to a normal core temperature after ~60min in the cooler environment and had relatively stable skin temperatures. Three quarters of the subjects were not well-hydrated upon entering the cooling center. Fifty-two percent of subjects had underlying health issues or co-morbidities that may exacerbate heat-health concerns. Findings will support improved guidance for heat relief network operators and respite centers regarding user safety, optimal resources to offer users, and duration of cooling center use to reach a safe and sustained body temperature.