In vitro experiments may not always reflect the natural behavior of an organism. To analyze the stress response of naturally acclimatized corals, we collected six Pocillopora acuta colonies living in the outdoor flow-through tanks (WT) at the beginning of September 2019, when water temperatures peaked at 29ºC in Kāneʻohe Bay (Fig. S3A). We let corals acclimate to 26ºC for two weeks to simulate our preconditioning experiment and then exposed them to acute heat stress (32ºC). The correlation of gene expression between WT and PC corals during acute heat stress was surprisingly high (Fig. 3, S3B) showing that corals’ molecular responses to acute temperature stress are similar to a natural temperature profile.