Smartphone location data show park use patterns in extreme heat (Los Angeles, California, USA)

• Parks are used slightly less during extreme heat days than paired control days. • Time of day and day of week are more important to park use than weather. • People from socially vulnerable areas are more likely to visit parks in less vulnerable areas than vice versa. • Planners should focus shade for cooling in areas of greater convenience (i.e. along daily routes) during extreme heat. Climate change, combined with the Urban Heat Island effect, will generate more frequent, intense extreme heat events. These events can induce heat stroke, organ damage, and death, especially in lower-income communities, communities of color, and people with chronic health conditions. Research demonstrates parks mitigate extreme heat and combat Urban Heat Island effects locally. To investigate how parks provide heat relief in Los Angeles County, California, we compared park use on extreme heat and control days from the summer of 2017. Our research uses big spatial datasets from smartphone devices to describe broad park use. We intersected anonymous smartphone geolocation data with county parks and census tract layers, then analyzed how the time of day, day of week, and park amenities influenced visitation. Then, we assigned users location-based social sensitivity indices using nighttime locations to explore demographic influence on park use. We found 1) park attendance decreased during extreme heat, 2) temporal convenience, rather than cooling amenities, influenced park use, and 3) users were more likely to visit parks with similar social sensitivity scores as their residence. Our results highlight the influence of social factors above extreme heat on park user behavior. We recommend that city planners focus on equitably and creatively distributing blue and green cooling amenities to communities (i.e. areas of convenience, common daily routes), rather than enhancing parks specifically.