A possible existence of a regular temporal trend superimposed over the durational pattern of individual segments is explored in read continuous speech in the western Slavonic language of Czech. A short text read by 75 speakers was used to ascertain whether the contextually conditioned temporal variation would allow any phrasal tendencies to manifest. The data were normalized against the speakers' characteristics and against the intrinsic duration of individual phones. The results indicate that while the linear trendlines are regularly declining, the most reliable partial trend is phrase-final deceleration. Three more general non-linear trends are identified.