Exposure to ecologically relevant thermal cycles (16–21°C) increased acute thermal tolerance (CTMax) compared to fish held at a stable acclimation temperature (16°C). Furthermore, we determined that exposure to a single elevated high temperature pulse (27°C) increased CTMax values by ~1°C but neither diel Tmin nor exposure to repeated diel pulses further elevated CTMax. Acclimation temperature has long been known to influence thermal tolerance in ectotherms (Beitinger et al., 2000); however, few studies have examined the effects of thermal cycles on CTMax (see Bennett and Beitinger, 1997; Currie et al., 2004; Fangue et al., 2011). In support of our findings, diel cycling did not affect CTMax in killifish (Fundulus heteroclitus) (Healy and Schulte, 2012) or the northern two-lined salamander (Eurycea bislineata) (Rutledge et al., 1987). In both cases, CTMax increased only when overall acclimation temperature was increased. Furthermore, Healy and Schulte (2012) suggest a complex association between variation in acute thermal tolerance and physiological (i.e. altered membrane fluidity) and environmental (i.e. photoperiod, hypoxia and time of day) processes. In nature, maximum temperature tolerance is poorly understood and thought to be a function of time, diel mean and ΔT (Wehrly et al., 2007) with periods of repeated sublethal stress capable of delaying mortality (Selong et al., 2001).