This part of ISO 15927 gives the definition and specifies methods of calculation and presentation of the monthly external design climate to be used in determining the design cooling load of buildings and the design of air conditioning systems. Depending on the building type, a range of parameters can be used to define the individual days of hourly or three-hourly data in each calendar month that impose a cooling load likely to be exceeded on 5 %, 2 % and 1 % of days. The parameters that are always used in the selection are dry-bulb temperature and total global solar irradiation (or sunshine hours). The daily swing in dry-bulb temperature, dewpoint temperature and wind speed and any other parameters relevant to particular buildings may also be included. Hourly peak values of dry-bulb temperature and dewpoint temperature are needed for the design of air conditioning systems.