One of the biggest challenges of climate change in developing countries is the lack of attention and action to adapt to its impacts. The duration and intensity of heatwaves aggravated by climate change significantly impact vulnerable communities with limited adaptive capacities. While European countries and the USA have implemented heatwave plans, there is a lack of attention and action in developing countries. This paper analyzes the adaptive responses to extreme heat in two cities in Northwest Mexico, Mexicali and Tijuana, through surveys in heat-vulnerable neighborhoods and semi-structured interviews with stakeholders. Results highlight a heavy reliance on air conditioning, a privatized form of adaptation that deepens economic burdens and reinforces environmental injustices, especially in marginalized communities. Respondents preferred behavioral changes as a short-term solution and wide support for increasing green areas. However, our results also show that strengthening knowledge of the symptoms of heat exhaustion, heat stroke, and first aid is needed to help people experiencing heat illness. Interviews revealed obstacles to public policy, including a lack of institutionalization and financing. They also show that an enhanced policy requires commitment, long-term planning, and interinstitutional agreements. The biggest challenges relate to socially marginalized groups, migrants, and people experiencing homelessness. Recommendations include developing equitable and inclusive green infrastructure, early warning systems, and community engagement. These findings set a valuable precedent for other dryland cities facing similar challenges to mobilize toward transformative adaptation, which is critical for sustainable cities.