This ecological study analyzed climate data and vector-borne disease surveillance records from 2015–2025 across five Southeast Asian countries. Temperature and rainfall anomalies were correlated with dengue, malaria, and chikungunya incidence. Findings reveal a significant association between rising minimum temperatures and extended dengue transmission seasons (r = 0.72, p < 0.01). Spatial clustering analysis identified emerging high-risk zones in previously low-incidence regions. The study emphasizes the need for climate-adaptive surveillance systems and cross-border collaboration to mitigate the evolving threat of climate-sensitive diseases.