This study identifies a set of warmth-activated neurons (AC neurons) in the Drosophila brain that play a critical role in temperature preference selection. AC neurons are activated just above the fly's preferred temperature and depend on dTRPA1, an ion channel that functions as a molecular sensor of warmth. Flies expressing dTRPA1 in AC neurons exhibit normal temperature preferences, while flies with reduced or eliminated dTRPA1 function choose warmer temperatures. This internal warmth-sensing pathway promotes avoidance of slightly elevated temperatures and works in conjunction with a distinct pathway for cold avoidance to set the fly's preferred temperature. The findings suggest that flies select a preferred temperature by using a thermal sensing pathway that triggers avoidance of temperatures deviating from the preferred range, providing a robust strategy for selecting an optimal temperature for survival. The study also highlights the potential of dTRPA1 as a genetically encoded tool for cell-specific neuronal activation and its role in other insect TRPA1s, which could be targeted for disrupting thermal preference in agricultural pests and disease vectors.This study identifies a set of warmth-activated neurons (AC neurons) in the Drosophila brain that play a critical role in temperature preference selection. AC neurons are activated just above the fly's preferred temperature and depend on dTRPA1, an ion channel that functions as a molecular sensor of warmth. Flies expressing dTRPA1 in AC neurons exhibit normal temperature preferences, while flies with reduced or eliminated dTRPA1 function choose warmer temperatures. This internal warmth-sensing pathway promotes avoidance of slightly elevated temperatures and works in conjunction with a distinct pathway for cold avoidance to set the fly's preferred temperature. The findings suggest that flies select a preferred temperature by using a thermal sensing pathway that triggers avoidance of temperatures deviating from the preferred range, providing a robust strategy for selecting an optimal temperature for survival. The study also highlights the potential of dTRPA1 as a genetically encoded tool for cell-specific neuronal activation and its role in other insect TRPA1s, which could be targeted for disrupting thermal preference in agricultural pests and disease vectors.