The diurnal range in surface temperatures (DTR = maximum - minimum temperature) has been widely used as one indicator of potential climate change. On hemispheric space scales DTR trends over about the last half-century tend to be decreasing. This paper analyzes regional scale trends in DTR for Mexico (1940--2001). Our principal finding is that in recent decades (post-1970) DTR trends over Mexico are positive as maximum temperatures are warming at a significantly higher rate than minimum temperatures. Regional land use and land cover changes (LCCs) are identified as potential forcing mechanisms responsible for at least part of the observed DTR behavior.