BACKGROUND: There have been reports indicating seasonal differences in the onset of chronic leg ulcers. The reasons for such seasonal fluctuations are not well understood. Therefore we decided to examine the seasonal incidence of chronic leg ulcers in our patient population, caused by chronic venous insufficiency (CVI) or mixed arterial and venous disorders, for any correlation with climatic factors. METHODS: We retrospectively analysed the data of 183 patients with chronic leg ulcers, evaluated the monthly and seasonal onset of the leg ulcers and investigated correlations between the incidence and climatic factors. RESULTS: The onset of chronic leg ulcers showed significant seasonal fluctuations with a decrease in summer and an increase in autumn-winter. The ulcer onset in the cold months, autumn and winter, was significantly higher (P Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 0.026) compared with spring and summer. Furthermore, in the bivariate correlation analysis of the variables temperature and ulcer onset, there was a statistically significant negative correlation between temperature and new ulcer onset. The colder the temperature was, the higher was the new ulcer onset with a correlation coefficient of -0.613 (P Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 0.034). CONCLUSION: The onset of chronic leg ulcers caused by CVI and mixed arterial and venous disorders in our patient population showed significant seasonal variations and demonstrated an inverse relationship to temperature. In summary, climatic factors appear to play an important role in the onset of chronic leg ulcers. Climatic factors may therefore need consideration in future clinical investigations and in the development of prophylactic therapeutic strategies.