Background <p>Climate-sensitive hazards such as extreme heat are increasing in frequency and severity. Protecting population health requires hazard-specific risk assessment, selection of potential interventions, and support for intervention implementation. This process typically takes several years, constraining health adaptation to climate-sensitive hazards. The investigators have developed an online decision support platform, CHaRT, that links evidence-based, location-specific heat-health risk assessment with transparent analyses of risk drivers and evidence-based risk reduction guidance for use in local health departments (LHDs). CHaRT’s effectiveness in supporting delivery of effective health interventions has not been evaluated.&#xa0;</p> Methods <p>LHDs are the organizational unit being studied. In this pilot randomized controlled trial, LHDs from the conterminous US will be recruited in coordination with the National Association of City and County Health Officials (NACCHO). Thirty LHDs will be selected at random from interested participants. Fifteen will be randomized to receive the intervention, a facilitated engagement with CHaRT, and 15 will receive the control, a package with information on heat vulnerability assessment and potential interventions. Intervention and control packages will be delivered simultaneously. Facilitated engagement will include an introduction to the tool, user exploration of the tool, elective inclusion of site-specific data into the tool, follow-up sessions to address additional questions, and discussion with investigators regarding planning and implementation needs. Pre- and post-study surveys will be used to assess CHaRT’s effectiveness using the RE-AIM (Reach, Effectiveness, Acceptability, Implementation, Maintenance) framework and by comparing each site’s intentions to implement specific interventions. After the trial, barriers and facilitators of the CHaRT platform’s implementation will be assessed through key informant interviews with the intervention group and analyzed using the Consolidated Framework for Implementation Research (CFIR).</p> Discussion <p>This study will allow investigators to evaluate the public health impact of a decision support platform and to identify barriers and facilitators of its implementation. The results will guide future research into strategies for increasing public health adaptation to climate change at the speed and breadth required.</p> Trial registration. <p>NCT06971978, <a href="https://clinicaltrials.gov/study/NCT06971978">https://clinicaltrials.gov/study/NCT06971978</a>, 5/14/25.</p>