Plants are able to sense and remember heat stress. An initial priming heat stress enables plants to acclimate so that they are able to survive a subsequent higher temperature. The heatshock transcription factors (HSFs) play a crucial role in this process, but the mechanisms by which plants sense heat stress are not well understood. By comprehensively analyzing the binding targets of all the HSFs, we find that HSFs act in a network, with upstream sensory acting in a transcriptional cascade to activate downstream HSFs and protective proteins.