To describe seasonal congestive heart failure (CHF) mortality and hospitalisations in Quebec, Canada between 1990-1998 and compare trends in CHF mortality and morbidity with those in France. Population cohort study. Province of Quebec, Canada. Mortality data were obtained from the Quebec Death Certificate Registry and hospitalisation from the Quebec Med-Echo hospital discharge database. Cases with primary ICD-9 code 428 were considered cases of CHF. Monthly CHF mortality was higher in January, declined until September and then rose steadily (p<0.05). Hospital admissions for CHF declined from May until September (moving averages analysis p<0.0001). Seasonal mortality patterns observed in Quebec were similar to those observed in France. CHF mortality in Quebec is highest during the winter and declines in the summer, similar to observations in France and Scotland. This suggests that absolute temperatures may not necessarily be that important but increased CHF mortality is observed once environmental temperatures fall below a certain "threshold" temperature. Alternatively better internal heating and warmer clothing required for survival in Quebec may ameliorate mortality patterns despite colder external environments.