<p>Precipitation and temperature extremes (PEs and TEs) are intensifying in many arid and semi-arid regions. Understanding these changes and their hydrological implications is increasingly critical for vulnerable basins. This study provides a comprehensive spatiotemporal assessment of climate extremes and their linkage with lake-level changes in the endorheic Urmia Lake Basin (ULB), northwestern Iran. Daily temperature and precipitation records from 17 stations (1990–2020) were used to compute 26 ETCCDI indices. Temporal trends and spatial patterns were examined using statistical and geostatistical approaches. Results show notable increases in heat- and dryness-related indices (TXx, TN90p, SU, GSL, CDD) and heavy precipitation indices (R10mm, R20mm, Rx1day, SDII, R99p). A structural break around 2008 indicated a transition toward more intense extremes, accompanied by a north–south contrast, with stronger flood tendencies in the north and intensified thermal stress in the south. TEs showed strong negative correlations with lake level (<i>r</i> =  − 0.66), whereas CWD displayed a moderate positive association (<i>r</i> = 0.50), indicating a stable climatic response to lake decline. Shifts in the behavior of the indices around the ecological threshold resulted from the influence of lake shrinkage on local climate. In linking coupled PEs and TEs with lake-level dynamics and associated feedbacks, this study provides an integrated framework that enhances our understanding of compound hydroclimatic risks and supports informed decision-making for the management of endorheic basins.</p>