Weather variables such as wind speed and direction, air temperature, humidity and rainfall may all be important factors in determining the course of a wide range of events. Weather monitoring is also important not just in defining the present climate, but also for detecting changes in climate and providing the data to input into models which enable us to predict future changes in our environment. The demand for weather data, usually on an hourly or more frequent timescale, has increasingly been met by the development and widespread deployment of automatic weather stations.