•The re-entrant jet induced cloud shedding is confirmed in hot water.•Whole stages of the cavity clouds developing and collapsing are presented.•Shedding dynamics of cavitation over a wide tempetature range are identified.•The thermal transition and increase-decrease trend of cavity length are analyzed. The effects of temperature on hydraulic cavitation dynamics are investigated under various operating conditions, in a close loop cavitation tunnel with a small-scale venturi type section. A systematic study is performed with temperatures varying between 24°C and 85°C, using a high-speed visualization system to observe the cavitating flow. The image processing methods provided in the paper present a quantitative comparison of the cavitation dynamics and structure development. The results show that the increase of the fluid temperature induces the growth of the cavitation volume up to about 55°C, thereafter an additional increase in temperature has the opposite effect. This evolution is interpreted as a competition between a Reynolds effect and the well-known thermal effect. Cavitation is more closely investigated within the temperature range 50°C - 65°C, to analyze the changes in the structure and the cavitation dynamics. For the prediction of thermal suppression head, the thermal effect parameter Σ which can be used empirically, is derived at the maximum cavitation length. This fluid thermodynamic parameter Σ(Ttrans) at the transition peak can be referred to to avoid the maximum cavitation aggressiveness induced vibration or erosion for thermos-fluids around the thermal transition temperature. Finally, the factors influencing cavitation length and shedding frequency are presented and analyzed.