Background and Objectives The seasonality and climatic relevance of epiglottitis have not yet been fully investigated in a population-based cohort. This study aimed to examine the seasonality of epiglottitis and explore associated climatic factors.Materials and Method In a retrospective cohort study using the Korean National Health Insurance claims database from January 2010 to December 2019, we identified patients with epiglottitis who claimed the following diagnostic codes as a principal or first additional diagnosis: International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) codes J0510, J0510.001 (acute epiglottitis without obstruction, epiglottitis not otherwise specified), and J0511 (acute epiglottitis with obstruction). We calculated the seasonal ratio as the ratio of the highest to the lowest number of patients per month to compare the degree of seasonality. In addition, the climate data points corresponding to each month were obtained. Thus, we analyzed the correlations between the monthly patient numbers for each disease and various climatic factors.Results There were seasonal variations in the number of patients with epiglottitis, which were highest from winter to spring and lowest in summer. The prevalence of epiglottitis was strongly correlated with the average temperature, ground temperature, relative humidity, precipitation, daily temperature range, and sunlight rate. Additionally, epiglottitis was most prevalent in the <9 age group before 2013, but after 2013, it was most prevalent in the 30–39 age group.Conclusion This large population-based study demonstrated clear seasonality and climatic association in patients with epiglottitis. Further studies exploring the detailed demographic factors affecting epiglottitis are required to address similar diseases more effectively.