Previous work has shown significant decreases of the diurnal temperature range (1941–80) across a network of 130 stations in the United States and Canada. In the present study, changes in monthly total precipitation at these same stations were related to the decrease in temperature range using various Monte Carlo. These tests indicate that factors other than those related to precipitation contributed to the decrease of daily temperature range. Further study of the mechanisms responsible for the decreased temperature range is warranted, based on these results. The decreased range may be one of the few pieces of evidence available in North America that is consistent with potential impacts of increased greenhouse gases and/or anthropogenic aerosols.