Central areas of London can be significantly warmer than the surrounding areas. These increased temperatures have an important impact on the cooling loads in buildings. Significant underestimates in the calculation of cooling loads can result from the use of rural temperature data, such as those for Bracknell given in CIBSE Guide A. This guide presents the results of long-term measurements of air temperatures at 80 sites around London and includes on a diskette a design tool to allow the designer to modify the Bracknell temperature data. The guide also outlines a range of techniques to reduce the effects of the heat island by careful design of the building and its surroundings. 36 pages + diskett - Temperature differences for London, By L Roche, A Sheridan, R Watkins