In the context of climate change, the global rise of temperature and intense heat waves affect plant development and productivity. In order to decipher the molecular and physiological mechanism established by plants to adapt to increased temperatures, we and others have designed different high-temperature regimes to mimic as much as possible temperature variations occurring in natura. This chapter outlines these thermotolerance assays employed to assess response to high temperature in Arabidopsis thaliana. We provide detailed guidelines, including plant age considerations and timing of heat application. Moreover, we introduce new findings showing that the addition of sucrose to the growth medium can artificially enhance thermotolerance, potentially masking stress-related phenotypes. These assays, which measure both basal and acquired thermotolerance, offer a framework for assessing plant heat stress responses in a reproducible and efficient manner. To illustrate some plant responses to these different regimes, we compare the response of mutants affected in the biosynthesis of the redox buffer glutathione with wild-type plants.