The focus of this document is on observations at surface meteorological observing stations. However, many of the principles will also be valid for other forms of observations, including upper-air observations and datasets based on mobile or remotely sensed platforms (for example, satellites, radar or drifting buoys). In particular, as many key remotely sensed datasets begin in the 1970s, it is recommended that, where feasible, the current climatological standard normal period (1981–2010 at the time of writing) be used for these datasets to allow comparison among different data forms on a consistent basis. Many of the principles will also apply to datasets involving locations or regions other than surface meteorological observing stations, such as area averages or points in gridded datasets.