The impact of climate changes on the urban environment may be assessed by calculating the modifications in energy production and consumption for such daily operations as heating and cooling. In this study climate changes in the southeastern Mediterranean (the area of Greece) were simulated for the year 2030 on the basis of specially constructed climatic scenarios which describe potential reductions in the emissions of greenhouse gases, and were, thereafter, used to calculate the heating and cooling degree days for the same year. The results show that the cumulative amount of heating and cooling degree days will decrease and increase, respectively, as compared to the respective amounts for the year 1990. In terms of the cooling degree days, it was found that the areas most affected were the Attica and central Macedonia regions, the Aegean islands and Crete, whereas in terms of the heating degree days, it was found that a large part of the country will require less energy for heating.