The circadian rhythm of peripheral cells can be regulated by diverse stimuli, including oscillations in hormones, metabolites and temperature. Saini et al. used bioluminescence assays to monitor the influence of physiologically relevant temperature oscillations on circadian gene expression in fibroblasts. Interestingly, 6–30-hour temperature cycles with stable fluctuations as low as 1–4˚C entrained the phases of circadian gene expression, even in cells that were in an opposite circadian phase before treatment. Among the studied temperature-regulated circadian genes, period homologue 2 (Per2) was the first to adapt to temperature-entrained phases, indicating that it is involved in the early response to phase transition. Temperature-sensitive genes are also involved in this response, as, for example, deletion of heat shock factor 1 (Hsf1) delayed the adaptation of circadian gene expression to temperature cycles.