Wind turbines have been erected in increasing numbers in Europe, the USA and elsewhere. In Europe Denmark has played a particularly prominent part in developing the technology and has installed a large numbers of turbines. The paper is concerned with the influence of the weather on the reliability of modern wind turbines and in particular the effect of wind speed. The prime objective of the work is to extract information from existing reliability data to draw conclusions about how the wind speed affects turbine reliability and which subassemblies in the turbine it affects the most. The purpose is to make information available to turbine manufacturers and operators so that the reliability of new wind turbine designs can be improved, particularly if they are to be installed offshore, where the weather is more inclement. Data are collected from Windstats for historic, maintained, Danish wind turbines and on-line data collected for the Danish weather. These data are used to analyse the reliability of wind turbines and their subassemblies in varying weather conditions from 1994–2004. The paper describes practical methods of extracting information from wind-turbine reliability data and shows how turbine design, turbine configuration, time and the weather can affect the extracted results.