Understanding long-term temperature behavior is essential for sustainable urban and environmental management in Somalia. Mogadishu, as a rapidly expanding coastal city, faces growing exposure to extreme heat events that threaten human comfort, health, and urban resilience. Yet, limited continuous environmental monitoring has constrained policy development. This study provides a comprehensive examination of historical temperature records from 2001 to 2025, offering new insights into climatic variability and thermal stress conditions in the Somali capital. Hourly temperature data were analyzed through time-series and statistical trend assessment methods. The Mann–Kendall test and Sen’s slope estimator were applied to determine the direction and magnitude of climatic trends. Heat-stress indicators, including the Heat Index and Discomfort Index, were used to classify thermal comfort levels. Seasonal and diurnal variations were visualized using anomaly and frequency plots. The analysis reveals a clear warming pattern over the 25 years, with an average temperature increase of approximately 1.2 °C and a noticeable increase in the frequency of hours exceeding 35 °C. The results show intensified heat stress conditions after 2015, particularly during the March–April season. The Discomfort Index indicates a substantial shift from the comfortable to the caution and danger categories, implying greater vulnerability among urban populations. These findings underscore the urgent need for climate-adaptive urban design, vegetation restoration, and reflective-surface technologies to mitigate rising thermal stress in Mogadishu.