This article focuses on the changes of climatic characteristics used in highway engineering following global climatic changes and the effect of these changes on pavement design. Along with traffic load, the climatic conditions belong to the external factors affecting the physical and mechanical properties of pavements. The climatic characteristics are defined by the average daily air temperature, the average annual temperature and the frost index (during winter period). In this article, measurements of air temperature from five meteorological stations in Slovakia during the period from 1971 to 2011 are evaluated. The calculated values of frost index provide good correlation dependence of frost index for a height above sea level. Using calculated values of frost index based on the long-term temperatures measuring can leads to reduction of pavement thickness. The using of the objectified correlation dependence of frost index is precondition for creating successful objectification of spending money on building roads, which belong to the financially demanding civil engineering structures.