Predicting plant phenological responses to future climate change is essential for effective ecosystem management and crop yield improvement. Muranka et al. found that the amplitude of diel transcriptomic rhythms showed seasonal switching with a sudden rhythm attenuation at 7°C and below in a natural population of Arabidopsis halleri subsp. gemmifera. In addition, field monitoring of plant size revealed growth arrest at similar temperatures. These results from in natura monitoring imply cooperation in the temperature-dependent regulations of circadian rhythmicity and growth, highlighting the importance of the circadian clock in predicting plant responses to climate change.