Plant growth and architecture are governed by both light and temperature in a coordinated manner. Therefore, it is unsurprising that light and temperature perception and signalling share common regulators and downstream responses. During thermomorphogenesis in higher ambient temperature plants elongate their hypocotyl and petiole length, dramatically altering their architecture. Here we reveal a new role of SUMO in the regulation of temperature perception and response in plants. We identified a SUMO protease that plays a critical role in the initial steps of higher ambient temperature perception. We have identified the targets for the SUMO Protease and demonstrate their role in thermomorphogenesis. We further found that SIM (SUMO-INTERACTING MOTIF)-SUMO interaction between target partners plays a pivotal role during this process and mutations in either the SIM or SUMOylation site/s leads to compromised thermo-responses.