Factors that associated with falls include muscle weakness and a loss of balance, and these are particularly serious risk factors in elderly. However, few reports have examined these risk factors for falls with respect to cold temperatures. In this study, we conducted a field survey of the indoor thermal environment and physical function in the elderly in the winter of 2017. First, a multiple regression analysis showed that in women, leg strength is significantly decreased in each room (room or non-living room) as the temperature decreases. In all samples (55 subjects), room temperature in the low walking speed group (<1.33 m/s) tended to be lower in each room compared with that of the control group (≥1.33 m/s). Finally, based on a path analysis, the minimum room temperature (i.e. the room temperature in the early morning) in each room had the greatest influence on factors related to the risk of falling.