A significant problem in the construction industry in the Republic of Croatia is the emigration of qualified domestic labor to countries with better working and living conditions. This results in the need to import labor from other countries. One of the main issues with importing labor is the lack of qualifications for performing construction work and the lack of adaptation to the climate in Croatia, which leads to decreased productivity and quality of construction projects, as well as difficulties in planning current and future projects. In addition to the fact that foreign workers, due to their lack of expertise, increase the risk of injuries on the construction site, their lack of adaptation to the climate can result in health problems if they do not follow the instructions of their superiors and can lead to project delays. Furthermore, there is the issue of language barriers and the inability to read blueprints, which further deteriorates the overall situation on the construction site. Croatian construction is forced to deal with the characteristics of non-acclimatized workers, the lengthy process of obtaining permits for their stay and work, and their quick departure to other EU member states where they are better paid and have better working conditions. Additionally, there is a loss of their work efficiency due to working in high temperatures. All of this ultimately results in project delays and increased costs, suggesting that cheap labor may not be economically viable. This paper presents the calculation of the project duration extension about the initial planned duration, depending on atmospheric influences and worker acclimatization.