This study formulated annual, monthly and hourly ambient temperature distributions for simplifying the calculation of cooling and heating degree-hours. In this regard, Turkey was selected as an application country, of which 79 cities were considered for modeling purposes. The temperature data over a period of 42 years were also utilized in the analysis. Similar outdoor distributions were categorized in the same group. The analysis results showed eight main annual distribution trends for the cities in Turkey. Such a detailed analysis and categorization for the outdoor temperature has been done for the first time in the literature. The outdoor temperature distributions are very useful tools for determination of heating and cooling loads while they enable the calculation of the annual-, monthly- and hourly-based degree-hours values. In this regard, a population-based outdoor temperature distribution concept was also introduced to the literature and tested for Turkey. One temperature distribution was achieved for Turkey with reference to population. (C) 2013 Elsevier Ltd. All rights reserved.