Climate and urban form explain shade patterns in U.S. cities

<title>Abstract</title> <p>Cities lack systematically measured shade data to guide heat planning, even though shade is more effective at reducing radiant heat load than greening and high-albedo surfaces, interventions for which data is widespread. Here, we treat shade as a measurable environmental service shaped by land-systems characteristics, analogous to how land systems science treats NDVI or albedo. Drawing from a national-scale, 1m resolution shade analysis across 330 + U.S. cities, analyzed at the census block group scale at 12:00 h, 15:00 h, and 18:00 h, we find that climate sets the floor for shade by constraining vegetative potential, and urban form sets the ceiling through building shade that dominates late-day shade production. Shade disparities are greatest at noon, but equalize later in the day as building shade increases. These predictable, generalizable patterns position shade for integration into land systems models and heat planning frameworks alongside temperature-based metrics.</p>