Environmental thermal patterning has been recognized as being intrinsically linked to fish physiology and performance (Helfman et al., 2009; Vasseur et al., 2014) and important for predicting the effects of climate change. We hypothesized that the nature of the thermal cycle, specifically nighttime temperature would dictate the physiological limits of juvenile Atlantic salmon. We found that our thermal cycles did initiate increases in CTMax and provided evidence of both cellular and metabolic stress. However, contrary to our expectation, we did not observe a correlation between the overall metabolic/cellular condition throughout a simulated heat event and the daily thermal minima. Thus, when fish are exposed to warming diel cycles approaching their critical temperature, we conclude that the diel thermal minima normally experienced by juvenile Atlantic salmon may not play a critical role in the ability of these fish to deal with extreme events. Notably, our experimental design, where we used a fixed maximum temperature, did not allow us to disentangle possible effects of the magnitude of diel thermal fluctuation from minimum nighttime temperatures. However, recent research from our group concluded that the nature of ecologically relevant diel thermal cycling (e.g. accumulated thermal exposure, magnitude, rate of change) did not significantly affect metabolism or the stress response in wild Atlantic salmon (Tunnah et al., 2017). Regardless, distinguishing between the importance of Tmin and ΔT is an important direction for future research.