Currently, the successful development of construction industry depends on the improved energy performance of buildings, structures and facilities, as well on the quality estimation of the outdoor climate. The problem of feasibly more accurate determination of energy consumption by climatic systems in buildings is a very high-priority task now because of decrease of energy and fuel sources and because of actualization of building standards in many countries. That is why it is very important to find simple but enough accurate dependences between climatic parameters in the heating as well as in the cooling seasons of a year. In the paper the modern principles accepted in different countries for the selection of the design climate information for the design of building envelopes and systems to ensure building microclimate are considered. Main shortcomings of the methods, including the concept of "typical year", are shown and the advantages of generating climate data arrays programmatically with the use of a pseudorandom number generator are described. Some results of the calculation of current temperature of the external air during the warm period of the year with different safety are presented using numerical modeling with Monte-Carlo procedure. The possibility of practical implementation of probabilisticstatistical principle of climatic data for some calculations relating to climatic systems and thermal regime of the building are shown. The comparison of the obtained values with the analytical expression for the normal distribution of random variables is presented and relationships for the selection of its main parameters according to the existing climatic manuals are proposed.