Given its potential for more realistic rendering and enhanced user experience, High Dynamic Range (HDR) imaging is raising a lot of interest both in industry and academia. In this context, efficient representation and coding techniques are needed, as HDR video entails significantly higher raw data rate. In this paper, we present a temporally constrained content-adaptive Tone Mapping Operator (TMO) in order to convert the input HDR video into a reduced bit depth video sequence which is then encoded using High Efficiency Video Coding (HEVC). As the proposed TMO simultaneously takes into account the statistical characteristics of the input frame while better preserving temporal coherence of the tone mapped video sequence, it leads to improved coding efficiency. Experimental results show that the proposed technique compares favorably with existing methods in terms of rate-distortion when using the HDR-VDP-2.2.1 quality metric.