Introduction: Regarding the association between climate, seasons and myocardial infarction, a cross-sectional study was carried out in Shiraz and Bandar Abbas in Iran. Methods: All patients with diagnosis of acute myocardial infarction living in Shiraz and Bandar Abbas were included in the study during 2011-2013. Demographic data were extracted from the patients' hospital records. Data were analyzed using descriptive statistics, student's t-test, and Chi-square test with SPSS software. Results: A total of 2626 patients were admitted with acute myocardial infarction of which 1546 were from Shiraz and 1080 from Bandar Abbas. Admission rate due to myocardial infarction was 0.12 in Shiraz and 0.24 in Bandar Abbas. In Shiraz, 35.2% were female and 34% in Bandar Abbas, Mean age of female patients was 65.68 years in Shiraz and 62.46 in Bandar Abbas while mean age of male patients in Shiraz was 60.39 years and 57.22 years in Bandar Abbas. Difference of admissions in 4 seasons was statistically significant in Shiraz, but not significant in Bandar Abbas (P>0.05). Seasonal variation of myocardial infarction had no correlation with gender or age of the patients. Conclusion: Incidence of myocardial infarction in Shiraz was half of the incidence rate in Bandar Abbas. In summer of low altitude humid areas, extra healthcare should be provided to high risk patients with coronary artery diseases, whereas this caution should be taken in high altitude areas with cold winter to minimize incident of myocardial infarction.