The modes of infection and transmission of Pneumocystis jiroveci remain unclear. This study explored the relationship between the incidence of infection and climatic factors. In total, 536 cases of P. jiroveci infection were identified in the period 1994-1998, with an inverse correlation between the incidence of Pneumocystis pneumonia and the minimum mean ambient temperature (Spearman correlation coefficient: r - 0.30; p 0.02; ARIMA model: r - 0.250, p 0.07). The highest number of cases occurred in winter (anova test, p < 0.05), and there was a clear season-related incidence of P. jiroveci infection.