Updated project metadata. Environmental factors such as temperature can modulate animal’s lifespan. However, the underlying mechanisms remain largely undefined. Through proteomic analysis of C. elegans at different time points (young adult, middle age, and old age) and under two temperature conditions (20°C and 25°C), we found that temperature affects C. elegans lifespan largely by modulating the proteostasis. Surprisingly, although animals live shorter at the higher temperature, we found that worms cultured at 25°C for one day at early adulthood promotes the protein homeostasis by decreasing the synthesis and increasing the degradation, suggesting the beneficial effects. Consistent with the finding, animals shifting from 20°C to 25°C for 24 hours between the larval L4 to adult Day 3 stages indeed live longer and are more resistant to stresses. Furthermore, we found that the one-day thermal induced lifespan extension is mediated by the FOXO transcriptional factor DAF-16. These results reveal an unexpected and complicated mechanism underlying the temperature effects on aging, which could potentially aid to develop strategies for treating aging related diseases.