Background: The role of temperature changes, as an environmental risk factor, in the human health status has been investigated in recent studies. Accordingly, the present two-year study was conducted to evaluate the incidence of myocardial infarction (MI) in warm and cold seasons in Ali-ibn Abi Talib Hospital, Rafsanjan, Iran.

Materials and Methods: In this descriptive and cross-sectional study, 264 patients hospitalized with MI during a two-year period (2013-2014) were included. Data on the participants were obtained from their electronic medical files and on the weather from the official Rafsanjan Weather Bureau station. The collected data was then analyzed using statistical tests including chi-squared test, Fisher's exact test, and logistic regression model in SPSS software.

Results: Data showed that 41.80% of MI occurred in hot weather, 14% in cold, and the remaining 37.12% in mild weather. According to the type of MI, 49.47% of non-ST elevation myocardial infarction (NSTEMI) and 44.44% of ST-segment elevation myocardial infarction (STEMI) occurred in very hot weather while 13.54% of NSTEMI and 18% of STEMI occurred in very cold weather. This difference was not significant.

Conclusions: Based on our data, MI had occurred mostly in hot weather and more than half of the cases were NSTEMI.