Intracellular Ca2+ is essential for diverse cellular functions.Ca2+ entry into many cell types including immune cells is triggered by depleting endoplasmic reticulum (ER) Ca2+, a process termed store-operated Ca2+ entry (SOCE).STIM1 is an ER Ca2+ sensor.Upon Ca2+ store depletion, STIM1 clusters at ER-plasma membrane junctions where it interacts with and gates Ca2+-permeable Orail ion channels.Here we show that STIM1 is also activated by temperature.Heating cells caused clustering of STIM1 at temperatures above 35℃ without depleting Ca2+ stores, and led to STIM1/Orail-mediated Ca2+ influx as a heat off-response (response after cooling).Interestingly, the functional coupling of STIM1 and Orai1 is prevented at high temperatures, potentially explaining the heat off-response.Importantly, physiologically-relevant temperature shifts modulates STIMl-dependent gene expression in Jurkat T-cells.Therefore, temperature is an important regulator of STIM1 function.