Between January 1932 and December 1941, Chiaverini and Rey (2) studied all deaths from congestive heart failure (CHF) confirmed by the city’s unique autopsy service. They concluded that most of the CHF deaths occurred during the winter, which in São Paulo runs from June to August. I examined the mortality data during a shorter period (July 1939 to December 1941), because there was better weather data, and confirmed Chiaverini and Rey’s results. In my analysis, CHF deaths were 28.8% higher during the winter months as compared with the summer months (December to February). Minimal monthly temperature (annual range 7.7 to 18.1°C) had a persistent association with CHF deaths (r = −0.31, p = 0.0456) after multiple linear regression analysis for humidity, hours of sunlight, temperature range and CHF mortality. These results from historic data are in concordance with a recent report analyzing coronary artery disease mortality in Hawaii (3), which is located at an equivalent latitude as São Paulo, but in the Northern Hemisphere. However, the most relevant finding from Chiaverini and Rey’s study is that most of the CHF cases were categorized as “nonatherosclerotic diseases.” During the 1940s in São Paulo (4), the etiology of CHF was rheumatic (23.6%), hypertensive heart disease (23.1%), atherosclerosis (20.6%), Chagas’ disease (10.8%) and syphilis (7.1%). Given these data, it is plausible to speculate that seasonal variations in cardiovascular mortality may be due to factors directly associated with impairment of myocardial contractility, such as arrhythmias and increasing blood pressure, rather than to factors more specifically related to rupture of coronary atherosclerotic plaque.