Detailed homogeneity assessments of daily maximum and minimum weather observing station data from Canada, the United States and Mexico enabled analysis changes in North American extremes starting in 1950. The measures of extremes assessed were primarily indices developed by the joint CCl/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices. Similar decreases in cold extremes and increases in warm extremes were found when examining the 10 th, 5th and 2.5th percentiles. Annual extreme cold temperatures are warming faster than annual extreme warm temperatures when the parameter measured is the actual temperature but cold and warm extremes are changing about the same when examined on a percentile or normalized basis. By any of several measures, heavy precipitation has been increasing in recent decades and the average amount of precipitation falling on days with precipitation has also been increasing. These changes in extremes are likely to impact natural ecosystems as well as agricultural and societal infrastructure.