Field surveys in Turkey indicate that a significant number of exterior wall assemblies in various regions of the country suffer from moisture degradation. These cases reveal that designers are in need for a climate scheme of Turkey, which indicates regions that require special provisions to prevent moisture degradation. Hence, this paper presents an approach for defining climate regions for Turkey. Initially, annual driving rain index (aDRI) based on monthly data is calculated and a driving rain map of Turkey is produced. Then, population-weighted heating degree-days (PW HDD) zones of Turkey are presented. Based on the aDRI and PW HDD zones, three climate regions of Turkey are established. Region I represents sheltered locations, i.e. locations which have aDRI less than 3. Region 2 represents locations (aDRI between 3 and 6 and PW HDD < 1600), which are exposed to moderate driving rain between September and the end of May when the mean temperatures are above zero. Region 3 includes locations (aDRI between 3 and 6 and PW HDD between 1601 and 2500) which are moderately exposed to driving rain all throughout the year when the mean temperature is well above zero. As a conclusion, the proposed climate regions suggest that the design of wall assemblies located at Regions 2 and 3 must incorporate special provisions to prevent moisture degradation. (C) 2005 Elsevier Ltd. All rights reserved.