Extreme heat events have become more frequent and intense due to climate change, leading to a rise in heat-related mortalities, especially in urban heat islands. But heat vulnerability (HV) is not uniform, as marginalized populations are often more impacted. What is less understood is how this vulnerability changes over time, especially as cities undergo uneven development or gentrification. Here we conducted a spatial-temporal analysis of Baltimore, MD, from 2000 to 2020, constructing a heat vulnerability index (HVI) to map changes over time. The purpose was to determine whether changes in socio-demographic/environmental variables, due to uneven development and gentrification, shifts HV. The results showed that HV decreased in 2010 but increased in 2020, with some areas improving while others worsened. This indicates that HV fluctuates in response to uneven development and gentrification. Our findings demonstrate the need for further research on how evolving social and environmental conditions shape HV over time.