Introduction: Over the past decades, fossil fuels and thermal power plants have consistently been among the major global issues, and their impacts on hydrological parameters and the environment have been extensively studied. Thermal power plants have both direct and indirect effects on human life. One of their positive effects is electricity generation; however, they also have significant negative impacts, such as air pollution. Global warming and climate change are among the consequences of burning fossil fuels and emitting greenhouse gases from thermal power plants.Thermal power plants, as one of the main sources of electrical energy generation, play a significant role in meeting electricity demand and promoting the economic development of countries. However, the use of fossil fuels in these plants can lead to various environmental consequences through the emission of greenhouse gases and atmospheric pollutants. Changes in temperature, alterations in precipitation patterns, reductions in humidity, and increased drought severity are among the potential consequences of climate change that can affect water resources, agriculture, and ecosystem sustainability. Investigating climate change in areas surrounding thermal power plants, particularly in arid and semi-arid regions, is especially important. Accordingly, this study investigates trends in climatic parameters in the vicinity of the Shahid Rajaee Thermal Power Plant in Qazvin Province, Iran, before and after the plant began operating in 1999 (1378 in the Iranian calendar).

Methodology: In this study, changes in precipitation depth, temperature, humidity, and wind were examined to identify temporal patterns of regional climate change and to determine differences in the trends of these parameters between two study periods. This research used regional meteorological data for 1984–2023 (1363–1402 in the Iranian calendar). The data were obtained from the Iran Meteorological Organization and corresponded to stations located approximately 7–35 km from the Shahid Rajaee Thermal Power Plant. To investigate changes in climatic parameters, precipitation trends were analyzed at seven stations, and temperature and humidity trends were examined at four stations. To compare climatic conditions before and after the plant began operating, the data were divided into two periods: 1984–1998 (1363–1377 in the Iranian calendar), representing the pre-operational period, and 1999–2023 (1378–1402 in the Iranian calendar), representing the post-operational period. Trend analysis was performed using the Mann–Kendall statistical test at daily, monthly, and annual scales. This method identifies the direction of trends in climatic parameters and is widely used to assess increasing and decreasing trends in environmental time series. In addition, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated using temperature and precipitation to determine drought conditions at each station.

Results: The analysis of meteorological data indicated that regional climatic trends changed following the commencement of operations at the Shahid Rajaee Thermal Power Plant. According to the reported findings, precipitation depth decreased by approximately 9% during the post-operational period. The most pronounced decreasing precipitation trends were observed at the Abyek, Naserabad, and Power Plant stations. Among the stations investigated, Naserabad was located closest to the power plant, underscoring the importance of examining the spatial patterns of precipitation changes in the vicinity of such facilities.

For temperature, the Mann–Kendall test indicated an increasing trend at all four stations during the post-operational period. The increase in temperature was reported to be approximately 10%, with an 11% increasing trend reported for all four stations. These findings indicate that the post-operational period was associated with rising temperatures at the stations under investigation.

The analysis of humidity revealed an approximately 5% decrease in humidity levels at all the stations examined during the post-operational period. Overall, the findings indicate that reduced precipitation and humidity, along with increased temperature, were among the most significant changes recorded in the area surrounding the Shahid Rajaee Thermal Power Plant when the two periods were compared.

Conclusion: The results of this study indicate that the period following the start of operations at the Shahid Rajaee Thermal Power Plant was associated with notable changes in certain regional climatic parameters. Reduced precipitation depth, higher temperatures, and lower humidity were among the most prominent patterns observed in the meteorological data. From an environmental perspective, the concurrent occurrence of these changes highlights the need to pay greater attention to the condition of water resources, the increased risk of water stress, and the vulnerability of regional ecosystems. In addition, the proximity of certain meteorological stations to the power plant, together with the observation of similar or different trends among these stations, underscores the need for a more detailed investigation into the relationship between spatial characteristics and climatic changes.

Ultimately, the findings emphasize the importance of continuously monitoring climatic parameters in areas surrounding thermal power plants and assessing the environmental consequences of their operations. The adoption of emission-reduction technologies, improvements in energy efficiency, optimal water resource management, and the gradual expansion of clean and renewable energy sources can help reduce the environmental pressures associated with electricity generation. Implementing these measures, especially in regions vulnerable to water scarcity, can support sustainable environmental management and strengthen climate change adaptation.