The model plant Arabidopsis thaliana responds to mild high temperature by increased elongation growth of organs to enhance cooling capacity, in a process called thermomorphogenesis. Our understanding of the genetic regulation of thermomorphogenesis has increased in recent years. However, hardly anything is known about molecular mechanisms outside A. thaliana and cellular signaling pathways have been underexplored. Therefore, we mapped changes in protein phosphorylation in A. thaliana and crops exposed to warm temperature. Based on these results, we identified and characterized a novel, functionally conserved signaling complex of MITOGEN-ACTIVATED PROTEIN KINASE KINASE KINASE KINASEs (MAP4KS) in warm temperature-mediated growth regulation in plants. This contributes to our understanding of warm temperature signaling, and can help guarantee food security under a changing climate