Seven years of winter survival data for winter wheat (Triticum aestivum L.) were collected on a plot at Ottawa, Ontario (45°23'N, 75°43'W). The site was low lying and subject to frequent winter flooding and ice sheet formation. The objective of the study was to gain insight into factors, including extreme weather conditions, which might affect winter survival. Two cultivars were planted in September. Crop establishment was measured in late fall and survival was measured in April of the following year. Hourly measurements of 0.05-m depth soil temperatures were made at grid points on the plot throughout the fall, winter and spring. Fall and spring soil moisture were measured on the plot as well as snow and ice depth at selected times throughout the winter. Detailed measurements of elevation were also taken. Meteorological data were available from the nearby weather site. In five of the seven years the survival rate was at least 70%. In the remaining two years, the survival rate was less than 20%. In one of the years, with survival of 18%, winter flooding and ice sheet formation were felt to be the cause of winterkill. In the other year, when survival on the plot was 17%, it was felt that extreme cold temperatures caused the winterkill. Winterkill due to cold temperatures was associated with conditions where there was little or no snow cover and air temperatures were in the range of -25°C. Winterkill due to flooding and ice sheet formation was associated with midwinter thaws, and rainfall followed by freezing temperatures. The risk of these extreme weather conditions was assessed.