This study examines the influence of temperature on inclinometer-based structural health monitoring (SHM) measurements in a steel railway truss bridge located in central–southern Chile. The objective is to characterize how thermal fluctuations shape sensor response, distinguish temperature-driven variability from non-thermal events, and contextualize these behaviors within regional climate trends. Historical data from triaxial inclinometers installed on three bridge piers were analyzed over a monitoring period exceeding one full seasonal cycle. The results show a strong and consistent correlation between temperature and inclination across all sensors, with daily and seasonal thermal cycles clearly reflected in the recorded structural response. Differences in thermal sensitivity were observed among the three piers, demonstrating that each sensor reacts uniquely to environmental loading conditions. Several deviations from temperature-driven patterns were also identified, including operational interventions, maintenance activities, and sensor replacement effects. These events highlight the importance of separating environmental influences from genuine structural behavior to ensure accurate diagnostics. To situate the analysis within a broader climatic context, regional indicators from ARCLIM were incorporated, showing projected increases in maximum temperature, annual thermal amplitude, and the frequency of warm days. These trends imply that temperature-induced variability in SHM measurements may intensify in future decades, reinforcing the need for climate-aware monitoring strategies. Overall, the findings emphasize that incorporating temperature trends and climate information into SHM interpretation improves the reliability of long-term assessments, reduces the risk of false alarms, and supports informed decision-making for maintenance and infrastructure resilience. The study provides practical insights for enhancing SHM workflows in regions experiencing significant climatic warming.