Changes in Rainfall Extremes in Ontario

There is a general consensus that climate change has impact on the intensity and frequency of rainfall events. However, very little research is available about the changes in short term rainfall extremes. The focus of this paper has been on the change in annual and monthly rainfall extremes in Ontario. The results indicate a greater variability (increase and decrease) among stations for shorter durations (15-min, 30-min, and 60-min). There is no obvious regional pattern with possible exception of increasing trends at north-western locations. The monthly rainfall extremes for the months of April and May in the Northwest region are decreasing, for May and October extremes in the southwest region and for April and May extremes in the southeast region are increasing. The August extremes for the southwest and southeast regions are decreasing, and the magnitude of decrease in the southwest region is almost double the magnitude in the southeast region. The decrease in August extremes seems to have a significant impact on the annual extremes in the southwest and southeast regions.