Construction works in the open air, in particular laying sewage systems, are susceptible to weather conditions. Weather conditions, such as very high or low emperatures, strong winds, intense and prolonged precipitation, interfere with work and they can even lead to cessation of construction. In consequence, the construction work lasts longer than originally assumed. On the other hand, it is impossible to alter weather. Therefore, it is vital to conduct a thorough identification of threats related to adverse weather conditions. This work makes an attempt to determine basic relationship between adverse weather conditions and the possibility of completing construction work according to a schedule. This analysis is a part of Schedule Risk Assessment. The findings show that the frequency of adverse weather occurrence is high and it affects schedule risk with special regard to air temperatures below -5°C and above 25°C. Thus, before starting construction, the probability of adverse weather conditions should be considered. Accurate identification of weather factors during the planning phase may help in accumulation of adequate reserves. Therefore, any unavoidable circumstances that are forced by adverse weather seem to be allowed in the schedule. This work focuses on air temperature, precipitation and wind because of their ...