This study investigates historical (1988–2017) and future (2020–2060) trends in extreme temperature and precipitation events across western and southwestern Iran. Daily observational data from 30 synoptic stations, along with outputs from CMIP6 climate models, were analyzed using 26 climate extreme indices based on CCL/CLIVAR recommendations. The Mann-Kendall test was employed to assess temporal trends. Results indicate a significant increase in warm temperature extremes (e.g., warm nights, warm days, and summer days) and a decrease in cold extremes (e.g., cold days, cold nights, and frost days) during the historical period, reflecting regional warming. Precipitation-related indices, including total annual precipitation, exhibited decreasing trends, though not statistically significant in many stations. Evaluation of the CNRM-CM6-1 model demonstrated strong performance in simulating daily temperatures but limited accuracy in precipitation projections. Future scenarios (ssp126 and ssp585) project a continued intensification of warm temperature extremes and further decline in cold extremes, while changes in precipitation extremes remain unclear. These findings underscore the critical need for adaptive water resource management, resilient agricultural planning, and informed climate adaptation strategies in response to projected warming and potential drought conditions.



This study investigates changes in extreme temperature and precipitation events in western and southwestern Iran during the historical period (1988–2017) and the future period (2020–2060). The data used include daily observations from 30 synoptic stations provided by the Iranian Meteorological Organization, as well as outputs from CMIP6 climate models. Using 26 extreme climate indices based on CCL/CLIVAR recommendations, temporal trends were analyzed through the Mann-Kendall test.

The results for the historical period indicate an increase in warm temperature indices—such as warm nights, warm days, and the number of summer days—and a decrease in cold temperature indices—such as cold days, cold nights, and frost days—suggesting a regional warming trend. In terms of precipitation, total annual rainfall and related indices have declined, although these downward trends were not statistically significant at many stations.

The evaluation of the CNRM-CM6-1 model shows that it performs well in simulating daily temperatures but has certain limitations in forecasting precipitation. Future projections under the ssp126 and ssp585 scenarios suggest that the upward trends in warm temperature indices and the downward trends in cold indices will continue, whereas precipitation extremes do not show a clear pattern of change.

These findings carry important implications for water resource management, agriculture, and climate adaptation policymaking, emphasizing the need for flexible and adaptive planning to cope with future warming and drought conditions.



In this study, to investigate changes in extreme climatic events in western and southwestern Iran, observational data on precipitation and temperature, along with outputs from CMIP model ensembles, were used to simulate these changes for the future period under two scenarios: RCP4.5 and RCP8.5. After collecting the data and conducting preliminary statistical analyses, extreme climate indices were calculated for both the baseline and future periods.

The trends of the indices were then assessed using the Mann-Kendall test and the Sen’s slope estimator. Finally, spatial maps of the intensity, duration, and frequency of the indices were generated.



The analysis of temporal changes in warm event indices in the region showed that, for most stations, warm indices such as warm nights, warm days, the number of summer days, and the number of tropical nights generally exhibit an upward, increasing trend.

The temporal changes in cold event indices indicated that, at most stations, cold indices such as cold days, cold nights, and the number of frost days generally show a decreasing trend.





The analysis of temporal changes in warm indices in the study area showed that, for most stations, warm indices such as warm nights, warm days, the number of summer days, and the number of tropical nights exhibited an overall increasing trend. The behavior of these indices is influenced by the region’s geographic location, topography, and environmental conditions.

The temporal variation of cold indices indicated a general decreasing trend in indices such as cold days, cold nights, and the number of frost days at most stations. Changes in these indices across the region are largely affected by terrain and elevation.

A key conclusion drawn from the overall analysis of warm and cold extreme indices is the dominance of a warming trend and the expansion of hot and dry climate types in the southern and southwestern parts of Iran.

The analysis of the frequency of precipitation extreme indices revealed a decreasing trend in annual total precipitation and daily precipitation extremes across various stations in the region.

The results of precipitation extreme indices for the period 2020–2060 under the ssp126 and ssp585 scenarios indicated that, overall, no consistent trend is expected for these indices under either scenario.

The findings for extreme temperature indices showed that future cold extremes in the study area are projected to decrease, while warm extremes are expected to increase. This upward trend in warm extreme indices is statistically significant for most indices across a substantial portion of the region.