The presentation will describe and compare the methods of determining cooling design conditions used by ASHRAE and the Australian Institute of Refrigeration, Air-Conditioning and Heating. A case study based on weather data for Brisbane will be used to illustrate the issues that arise. One issue is the usefulness of the 3-hourly temperature observations archived in International Weather Office records compared to the hourly observations required by the ASHRAE method. Another issue is the use of daily maxima, which have been archived for over 100 years at many Australian locations. Daily data can easily be used to find trends of global and/or urban warming that cannot readily be seen in detailed hourly datasets. The presentation will address the use of cumulative distribution functions to select the design dry bulb and coincident wet bulb temperatures required to size cooling and dehumidification systems.