INTRODUCTION AND OBJECTIVES: Some atmospheric features have been linked to the triggering of myocardial infarction. Because data from the Temperate-Mediterranean is scarce, we sought to study whether meteorological parameters influence the incidence of ST-elevation myocardial infarction (STEMI) as confirmed by primary percutaneous intervention in a city with temperate weather (Porto, Portugal). METHODS: Retrospective analysis of a series of STEMI-patients from January 2010 to December 2017. Temperature (T), relative humidity (RH), precipitation, and atmospheric pressure were obtained from a government-led institute. We utilized a generalized linear model (GLM) with a Poisson distribution, where a series of models with multivariable analysis were computed. The effects (GLM coefficients) are presented as excess relative risk (ERR). RESULTS: One thousand and four consecutive STEMI-patients were included. The most important predictors of STEMI were Tmin two days before (for 1°C drop ERR=1.9%, p=0.009) and a 1% increase in RH three days before (EER=0.7%, p=0.006). Conversely, the same increase in RH the day before reduced the relative risk (EER=-0.6%, p=0.023). Temperature range, atmospheric pressure and precipitation had no impact on STEMI incidence. CONCLUSION: In a Temperate-Mediterranean city hot or cold temperature extremes, temperature drop and relative humidity had a significant impact on the occurrence of STEMI.