Heat tolerance classification criteria require population‐specific thresholds for accurate assessment of acclimation state in adults. - Bowie, Jacob S.; Szymanski, Michael R.; Struder, Jeb F.; Filep, Erica M.; Morrissey‐Basler, Margaret C.; Brewer, Gabrielle J.; Thornton, Staci N.; Mahoney, Kyle J.; Sekiguchi, Yasuki; Kwon, Oh Sung; Chon, Ki; Casa, Douglas J.; et al. (Physiological Reports, 2026)