Concentrations of fungal and bacterial bioaerosols were measured during winter. Environmental parameters such as temperature, relative humidity, ultraviolet irradiation intensity, and the amount of snowfall precipitation were also measured with bioaerosol concentrations. Experimental results show that significant amounts of culturable fungal bioaerosols exist in the air during winter. The amount of fungal bioaerosols present in winter is comparable with that recorded in summer. In contrast, few culturable bacterial bioaerosols were detected in the air during winter. This quantitative result can be used to explain patterns of diseases that occur in winter. In addition, the effects of environmental factors on bioaerosols in winter were analyzed. (C) 2015 Elsevier Ltd. All rights reserved.