Considering the South American context and particularly the Chilean case, climatic effects and atural risks acquire a particular emphasis due to the extreme conditions in many locations. Thus, in terms of the importance of preserving the architectural heritage of our towns and cities, it is essential to develop specialized methodologies to support decision-making by professional experts in heritage conservation, especially in developing countries and also considering the effects of external hazards related to climatic and natural variables, as in the case of Chile, where there are few studies related to the preservation of local heritage including climatic variables and its current conditions, this kind of approach is essential. Hence, due to the uncertainty related to the prediction of future climate conditions, a new fuzzy inference system is proposed aimed at predicting climatological variables and their effect on heritage infrastructures. This new digital model is based on previous fuzzy systems experiences and on the analysis of an earlier Delphi study, which was carried out to explore the climatic variables in their effect on the conservation of buildings. Mainly, the new digital system based on fuzzy logic focuses for the first time on evaluating five climatic variables (precipitations, temperature, wind, solar radiation and relative humidity) regarding the preservation of buildings and considering the specific characteristics of each site. This study establishes a new fuzzy logic method, which allows a systematic classification of buildings’ performance and their efficacy based on climatic conditions. The novelty of this research work concerns an original fuzzy inference system, which can model information with uncertain degrees, which should be regarded as new support for the decision-making process concerning heritage building performance and climatic conditions in South America, particularly Chile. This research provides new advances in terms of the influence of climatic indicators on the functional performance of heritage buildings. This type of work is a new contribution towards predicting the deterioration of buildings in different climatic situations.