As climate change increases the frequency, duration, and intensity of extreme heat events, inequitable access to thermally comfortable outdoor environments has become a pressing urban planning and public health challenge. In dense cities, limited shade can amplify heat exposure and compound existing social and health inequities. This study develops a spatio-temporal framework to identify gaps between shade supply and demand. We introduce the concept of shade deserts, defined as areas where shade availability (supply) fails to meet the need for shade (demand). Shade supply is quantified using hyperlocal, 1-metre resolution microclimate simulations that capture temporal variations in shadow patterns throughout the day. Shade demand is estimated by integrating the Universal Thermal Climate Index (UTCI), a physiological indicator of heat stress, with measures of physical vulnerability. We further identify persistent shade deserts and shade oases, referring to locations that consistently remain underserved or well-served. Applying this framework to Vancouver, BC, Canada, we identify a clear east-west divide, with persistent shade deserts concentrated in the eastern neighbourhoods and shade oases more prevalent in the west. Statistical analyses reveal that the presence of shade deserts is significantly associated with socioeconomically disadvantaged populations. The proposed approach and findings from this study provide a practical tool for planners and public health practitioners seeking to prioritize interventions, enhance climate resilience, and promote more equitable urban environments in the face of intensifying climate change.