Abstract The evolution of moist static energy (MSE) is widely used to understand the organization and propagation of the Madden‐Julian Oscillation (MJO). Past studies, largely based on reanalysis or short‐term observations, have highlighted humidity as the dominant driver of MJO evolution. Using 14 years of bias‐corrected radiosonde observations from the Department of Energy—Atmospheric Radiation Measurement Facility site at Manus in the western Pacific, we show that temperature has a non‐negligible influence on the vertically integrated MSE during MJO’s transition from suppressed to active phase. Specifically, during the transition phase in boreal winter (spring), ∼48% (∼31%) of the vertically integrated MSE anomalies are attributed to temperature anomalies. This temperature contribution is confined to the mid‐ and upper‐troposphere, where temperature and MSE anomalies exhibit a strong correlation. These findings have important implications for MJO theory and provide new constraints for evaluating MJO transition processes in models.