Background: The cold season seems to be a trigger for atrial fibrillation (AF). Some reports are controversial and demonstrate variability according to the climatic characteristics in different regions.

Objective: To analyze whether meteorological factors contribute to seasonal variation of exacerbation of AF diagnosed in patients referred to the emergency department (ED) of our hospital.

Methods: We retrospectively reviewed medical data of consecutive patients admitted to the ED with symptomatic acute onset AF from 1 January 2016 to 31 December 2018. We recorded the mean monthly outdoor temperature, barometric pressure, and relative humidity during the study period.

Results: During the study period, 1492 episodes of AF were recorded. New onset AF were 639 (42.8%) and paroxysmal atrial fibrillation (PAF) were 853 (57.2%) (P = 0.03). The number of overall admission of AF episodes was not distributed uniformly through the year. Incidence of AF episodes peaked during December and was lowest in June (P = 0.049). Of 696 episodes (46.6 %) the patients were hospitalized and for 796 (53.4%) the patients were discharged (0.01). The number of hospitalizations was not distributed uniformly through the year (P = 0.049). The highest number of hospitalizations happened in December and the lowest in May. Outdoor temperature and barometric pressure (but not relative humidity) may mediate a monthly fluctuation in AF episodes with highest number of ED visits in December and the lowest in June.

Conclusions: Meteorological conditions influence exacerbation of AF episodes and hospitalization. Outdoor temperature and barometric pressure may mediate a monthly fluctuation in AF