The number of heating and cooling degree-days is an impact indicator, and it is important to know the total number to understand the energy required to heat or cool buildings. If the outdoor air temperature is above 15 °C, heating is unnecessary. Heating  costs are directly proportional to annual Heating Degree Days (HDD). HDD is also used to compare winter severity to previous and long years.

If the heating and cooling day-degrees in Turkey are considered for 129 stations in Turkey; while the Heating Day-Degrees for many years (2007-2020) are 2041 Day- Degrees, the Cooling Day-Degrees are 362 Day-Degrees^[28]_.

MAP 1- AVERAGE HEATING DAY-DEGREES FOR 2007-2020 IN TURKEY

Source: The Ministry of Environment, Urbanisation and Climate Change, Turkish State Meteorological Service; 2021

MAP 2- TÜRKİYE 2020 YILI ISITMA GÜN-DERECELERİ

Source: The Ministry of Environment, Urbanisation and Climate Change, Turkish State Meteorological Service; 2021

While the average Heating Day-Degrees in 2020 in 129 centers in Turkeywere 1947 Day- Degrees, the Cooling Day-Degrees was realized with 404 Day-Degrees^[29].

MAP 3- AVERAGE COOLING DAY-DEGREES FOR 2007-2020 IN TURKEY

Source: The Ministry of Environment, Urbanisation and Climate Change, Turkish State Meteorological Service; 2021

MAP 4- COOLING DAY-DEGREES FOR 2020 IN TURKEY

Source: The Ministry of Environment, Urbanisation and Climate Change, Turkish State Meteorological Service; 2021

Analyzing the situation in Europe (EU-28 excluding Cyprus, Liechtenstein, Norway and Switzerland), we find that annual population-weighted heating day degrees (HDD) decreased by  percent 6 between the periods 1950-1980 and 1981-2017. Annual population-weighted cooling day degrees (CDD) increased by percent 33 between the periods 1950-1980 and 1981-2017^[30].